deck: filter mod moves to FILTER ENV, cell runs centre in their reserves, two-segment toggles become single buttons, deck focuses its overlay

src/core/instrument/CLAUDE.md

@@ -218,9 +218,14 @@ automatable parameters."* It rejects the precedent, not one instance of it.
 ### The envelope overlay — one graphical surface, every envelope (S-VIEW, extended)
 
 The overlay draws ONE envelope over the Sample view's hero waveform, and WHICH one is a
-transient editor choice: each envelope deck (amp, pitch, filter) carries a corner radio, at
-most one is overlay-active, and **none is a valid resting state — the editor opens there.**
-Never persisted; it selects what is drawn, not what is played.
+transient editor choice: **clicking anywhere in an envelope deck (amp, pitch, filter) — panel,
+knob or button — focuses that deck's overlay**, and the focused deck takes an `AccentPrimary`
+border. At most one is overlay-active, and **none is a valid resting state — the editor opens
+there**, reached by clicking a control surface outside the three decks. Focus SETS rather than
+toggles, so editing the deck you selected cannot deselect it; the overlay itself neither steals
+nor clears focus for the same reason. Never persisted; it selects what is drawn, not what is
+played. *(The per-deck corner radio this replaced is gone; MASTER keeps the corner slot for its
+passive gain-reduction lamp.)*
 
 **The overlay is directly editable — draggable nodes (SETTLED, S-VIEW-F2), plus a round
 mid-segment knot per sloped stage that sets that stage's curve exponent.** A node drag, a
@@ -344,7 +349,7 @@ anything for a trigger shape.
 - `param_taper` — THE norm↔value tapers every variable control shares, and the modifier vocabulary its drag surfaces read: the stage-time shifted-log (and `kStageTimeMaxSeconds`, the ONE home of the stage-time ceiling that `envelope_overlay`'s `kGateStageMaxSeconds` and `deck_values`' `kEnvTimeMaxSeconds` alias), the centre-expanded semitone-depth map, `DragModifiers`/`kFineDragScale`/`fineDrag`, the `UnitCategory` axis, and the four whole-unit snaps Shift applies. Extracted from `deck_values` because it has THREE consumers in two dependency layers — the knob's needle (`deck_values`), the AHDSR schematic axis and its drag inverse (`envelope_overlay`/`envelope_edit`, which sit *below* `deck_values`), and the VST3 host's `toPlain`/`toNormalized`. **Three functions that agree today is a defect, not an implementation choice**; solving the include edge by copying the map is the specific mistake this exists to prevent. Both maps resolve their output onto a fixed decimal quantum, which is what makes "every default has an EXACT normalized preimage" a structural guarantee rather than a libm coincidence — the header states the argument; the converse round trip at an arbitrary norm is explicitly NOT required.
 - `param_slider` — parameter control-panel: vertical stack of TOGGLE (two-segment selector) and SLIDER (horizontal track) rows; maps normalized value to/from handle pixel. `knobDragValue` is the knob's grab-anchored absolute drag law and applies Ctrl's rate — but not Shift's snap, whose whole unit is a property of the control's unit category this module does not know.
 - `embed_strip` — compact single-row control layout for embed mode in the track FX chain.
-- `knob_deck` — pure knob-deck layout + hit-test (FB1): group-box / caption-row / compact-toggle / knob-cell geometry, the categorical row law, `DeckLayout` / `DeckHit`. Mirror of `action_bar`/`param_slider`; no LICE or REAPER types. **Row membership is a property of the GROUP (`DeckRow`), never a wrap outcome** — the greedy whole-group wrap it replaced is gone, and the layout is the specified arrangement by construction at every width. Both categorical rows are justified SPACE-BETWEEN inside the row block (slack divided equally among the (n−1) gutters, integer residue to the leftmost, never below `kDeckGroupGap`, decks never stretched); a `DeckRow::Spanning` group is right-anchored OUTSIDE that block at `kDeckSpanningH` and takes no part in either row's justification. Below the width the block needs, gutters floor and the row overruns right rather than wrapping — the editor clamps its window above that, so the degrade only has to be defined. A spanning group reads `cellIds` DOWN, one fixed `kDeckCellW` slot per declared id at successive row baselines (reserves advance the slot), plus an optional full-height readout `column`; the run-division law below is horizontal only, and applying it vertically would stretch a lone knob over the whole box. A `DeckRadioDesc` may be `passive` — same corner slot, skipped by the hit-test, so a readout lamp cannot grow a gesture. Carries a SECOND hit-test, `hitTestKnobFace`, resolved against the drawn CIRCLES rather than the cell: a double-click reset is aimed at a dial, so the label band and the cell margins must miss where a drag grab deliberately does not, and only a radial resolve can tell the inner curve dial from the outer ring it sits inside. The deck's width budget at the editor's floor — the row block, the spanning deck's reserve, and what drives the floor — is declared and reasoned at the constants themselves (`knob_deck.h`; the ceiling itself now lives in `sample_bands.h` as a window fact); every group's categorical row is `deck_groups`' `deckRowFor`. A group carries TWO caption-toggle slots, laid right-to-left: the second exists because a group whose knob row is wider than its caption row has caption slack a toggle can occupy for free, where a `rowToggle` widens the GROUP and is charged against that budget — which is why the env decks' mode toggles ride the caption row. **A group's cell run is a RESERVED WIDTH, not a fixed cell size**: a `-1` id reserves one cell's width without a cell, and the cells present divide the whole run between them at one uniform integer width (residue in symmetric end margins). That is what lets a mode flip drop controls from a face — Trigger's AMP and FILTER ENV lose their Sustain/Release stages — without either reflowing the deck or leaving dead slots in the box; a face with fewer controls simply gets roomier cells. Do not reintroduce fixed-width cells with blank slots.
+- `knob_deck` — pure knob-deck layout + hit-test (FB1): group-box / caption-row / compact-toggle / knob-cell geometry, the categorical row law, `DeckLayout` / `DeckHit`. Mirror of `action_bar`/`param_slider`; no LICE or REAPER types. **Row membership is a property of the GROUP (`DeckRow`), never a wrap outcome** — the greedy whole-group wrap it replaced is gone, and the layout is the specified arrangement by construction at every width. Both categorical rows are justified SPACE-BETWEEN inside the row block (slack divided equally among the (n−1) gutters, integer residue to the leftmost, never below `kDeckGroupGap`, decks never stretched); a `DeckRow::Spanning` group is right-anchored OUTSIDE that block at `kDeckSpanningH` and takes no part in either row's justification. Below the width the block needs, gutters floor and the row overruns right rather than wrapping — the editor clamps its window above that, so the degrade only has to be defined. A spanning group reads `cellIds` DOWN, one fixed `kDeckCellW` slot per declared id at successive row baselines (reserves advance the slot), plus an optional full-height readout `column`; the run-division law below is horizontal only, and applying it vertically would stretch a lone knob over the whole box. A `DeckRadioDesc` may be `passive` — same corner slot, skipped by the hit-test, so a readout lamp cannot grow a gesture. Carries a SECOND hit-test, `hitTestKnobFace`, resolved against the drawn CIRCLES rather than the cell: a double-click reset is aimed at a dial, so the label band and the cell margins must miss where a drag grab deliberately does not, and only a radial resolve can tell the inner curve dial from the outer ring it sits inside. The deck's width budget at the editor's floor — the row block, the spanning deck's reserve, and what drives the floor — is declared and reasoned at the constants themselves (`knob_deck.h`; the ceiling itself now lives in `sample_bands.h` as a window fact); every group's categorical row is `deck_groups`' `deckRowFor`. A group carries TWO caption-toggle slots, laid right-to-left: the second exists because a group whose knob row is wider than its caption row has caption slack a toggle can occupy for free, where a `rowToggle` widens the GROUP and is charged against that budget — which is why the env decks' mode toggles ride the caption row. **A group's cell run is a RESERVED WIDTH, and the cells present are CENTRED in it at their natural `kDeckCellW`**: a `-1` id reserves one cell's width without a cell, and the reserve is paid for in symmetric end margins, never in wider cells. That is what lets a mode flip drop controls from a face — Trigger's AMP and FILTER ENV lose their Sustain/Release stages — without either reflowing the deck or stretching the knobs off their pitch; only the reserve COUNT matters, so where a `-1` sits in `cellIds` is free. Two rejected laws, recorded so they are not re-proposed: dropping the reserves (reflows every neighbour on a mode flip, which is what the reserves exist to prevent), and dividing the run between the cells present (the retired law — it handed a reduced face 90–100 px cells). A SPANNING group is the one place a reserve's position still matters, because there it advances a fixed slot.
 - `deck_values` — the deck's control-id ↔ parameter-set BINDING and its display units, split
   from the editor shell on the same axis `deck_groups` was split from `knob_deck`: `deck_groups`
   says which controls exist, this says what each one's value MEANS. Holds `deckParamNorm` /
@@ -363,7 +368,7 @@ anything for a trigger shape.
   parameter set does not carry (key-track, voice count, master gain, preview velocity) and the
   labels for them.
 - `master_meter` — the MASTER column's interior, split from `knob_deck` on the axis `sample_chrome` has to `sample_bands`: that says where the column is, this lays out inside it (22 px numeral gutter · 4 · 36 px bar field) and holds the per-instance UI state the bars draw from. `kMeterColumnW` is the SUM of those three, exported so `deck_groups`' MASTER descriptor reserves exactly what the interior consumes — the column is banked to grow, and a reserve that did not track it would underfill or overrun silently. **Bar count takes a RESOLVED `LaneSplit`, the same value `waveform_view`'s `resolveLaneSplit` answers** — a mono source under stereo mode is dual-mono, and two identical bars would be a lie. Also owns `meterTickNumeralled` (the spec-pinned 0/−12/−24/−36/−48/−60 numeral set, beside the tick step it derives from), `meterNumeralRect` (bottom-clamped, so the floor tick's numeral cannot hang out of the gutter), and `meterSingleLaneState` — the one bar folds both channels PER FIELD, never picking a whole channel by level. Composes `engine/meter_ballistics` per channel and gives the gain-reduction lamp the peak tick's own hold-then-release, without which a catch smaller than 20 dB × the UI period is dark again before it has been drawn twice; the audio thread's clip flag is ORed in because it is the only latch that sees every block. `meterDrawEqual` is what lets the UI tick repaint on change alone.
-- `deck_groups` — also home to `deckParamCommit` and `liveCommitFor`, the editor's whole commit-tier routing decision (see "Live parameter delivery" above), and to `OverlayEnv` + `nextOverlaySelection`/`overlayEnvEnabled`/`overlayEnvInert`, the whole overlay-selection state machine (exclusivity, the none resting state, and which selections a disabled or DRAWN group makes inert); WHICH groups the Sample face's deck carries, split from `knob_deck`'s HOW they lay out: the `DeckParam` control-id space (the editor's `ParamControl` is an alias of it), the `DeckGroupId` list, `sampleDeckGroups` in signal-flow order (**pitch → filter → amp**, then velocity/voice/master), and the deck's bipolar-knob law. Reads `PlayMode` for the AMP group's Gate/Trigger face, which is why this and not `knob_deck` is the module that touches the engine's value layer. Also home to `CurveTarget` + `curveTargetFor` — the VELOCITY group's three cells are popup openers, not dials, and that predicate is the ONE place they are named, so paint, hit-test routing and the popup's title all agree. MASTER is reserved for post-voice-mixer concerns, which is why the curves sit in their own group immediately left of VOICE rather than there; it now discharges that reservation as the double-height bus deck — gain, the limiter enable, one reserved slot, the meter column and the GR lamp. FILTER's `Band|Notch` rides its caption slack rather than the knob row: that is the −92 px that makes the SOUND row fit its block, and putting it back breaks the fit. VOICE's `Retrig|Legato` deliberately stays in the knob row — VOICE's caption row is the binding side, so moving it there makes the group 226 rather than 164.
+- `deck_groups` — also home to `deckParamCommit` and `liveCommitFor`, the editor's whole commit-tier routing decision (see "Live parameter delivery" above), and to `OverlayEnv` + `overlayEnvForGroup`/`overlayEnvEnabled`/`overlayEnvInert`, the whole overlay-FOCUS state machine (which deck names which envelope, the none resting state, and which selections a disabled or DRAWN group makes inert); WHICH groups the Sample face's deck carries, split from `knob_deck`'s HOW they lay out: the `DeckParam` control-id space (the editor's `ParamControl` is an alias of it), the `DeckGroupId` list, `sampleDeckGroups` in signal-flow order (**pitch → filter → amp**, then velocity/voice/master), and the deck's bipolar-knob law. Reads `PlayMode` for the AMP group's Gate/Trigger face, which is why this and not `knob_deck` is the module that touches the engine's value layer. Also home to `CurveTarget` + `curveTargetFor` — the VELOCITY group's three cells are popup openers, not dials, and that predicate is the ONE place they are named, so paint, hit-test routing and the popup's title all agree. MASTER is reserved for post-voice-mixer concerns, which is why the curves sit in their own group immediately left of VOICE rather than there; it now discharges that reservation as the double-height bus deck — gain, the limiter enable, one reserved slot, the meter column and the GR lamp. FILTER's `Band|Notch` rides its caption slack rather than the knob row: that is the −92 px that makes the SOUND row fit its block, and putting it back breaks the fit. VOICE's `Retrig|Legato` deliberately stays in the knob row — VOICE's caption row is the binding side, so moving it there makes the group 226 rather than 164.
 - `spline_edit` — THE point-editing grammar, and the one place it is written down: left-click grabs a node and adds one in empty space, right-click deletes, control-click toggles hard/smooth. Both spline consumers — the velocity-curve popup and the spline EG overlay — route their mouse-down through `resolveSplineEdit`, so the two cannot drift into two grammars. The endpoint and point-count rules are NOT restated here: `deletePoint` and `addPoint` own them, and the caller applies the resolved action to the curve. Also home to `splineOverlayBox`, the contour's mapping box inside the waveform overlay — the FULL area, no inset, so the drawn contour stays 1:1 with the sample's time axis. Spline points are excluded from `param_taper`'s Shift/Ctrl modifier law like waveform markers are: a point is a normalized position with no displayed unit, and control-click there is already claimed by the hard/smooth toggle above.
 - `curve_popup` — pure curve-popup geometry + dismissal test (FB1): centered sheet over the Sample face — width/height clamps, title row, Close button rect, curve-box rect, outside-sheet dismissal test. Mirror of `overflow_menu`; no LICE or REAPER types.
 - `envelope_overlay` — pure staged-envelope→polyline geometry for the Sample-view overlay (read from `envelope_overlay.h`): maps a `StageEnvelope` to a polyline inside a rect under whichever of TWO layout policies its `EnvKind` selects — an AHDSR draws a bounded param-domain schematic with its release RIGHT-ANCHORED to the canvas edge, an AHD draws 1:1 over the waveform's own time axis — plus a round mid-segment knot on every sloped stage that has a duration. Every vertex clamped in-canvas. Shares the `EnvNode`/`StageEnvelope`/`timeToX`/`levelToY` vocabulary with `envelope_edit` so the drawn handle and its grab region agree pixel-for-pixel. No VST3/REAPER/LICE types at the boundary.