Γ-W1-T1 review fixes: mode-independent taper rounding, sharper drag-step test, reset-sweep verifies stored fields

Swap nearbyint for std::round (MXCSR-independent); derive the finest-drag test
from the editor floor, not the knob; verify resets against fields, not norms;
record the spline-point modifier exclusion.

src/core/instrument/CLAUDE.md

@@ -334,7 +334,7 @@ anything for a trigger shape.
   parameter set does not carry (key-track, voice count, master gain, preview velocity) and the
   labels for them.
 - `deck_groups` — also home to `isLiveDeckParam` 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.
-- `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_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.
 - `envelope_edit` — pure node hit-test + pixel-delta→clamped-param inverse map for the draggable envelope nodes and their curve knots (read from `envelope_edit.h`): `nodeAtPoint` resolves a grab to the nearest node within a pick radius (Chebyshev distance, draw-order tie-break, knots appended last so a coincident endpoint handle wins); `resolveNodeDrag` maps a pixel delta since grab to a new `StageEnvelope` under the same caller-supplied per-param clamp bounds the knobs use — a drag can never produce a param a knob couldn't. Mirror of `card_drag`/`waveform_view`; the inverse of `envelope_overlay`'s params→polyline forward map, so node-drag, knot-drag and knob-edit read/write one shared model and can never diverge.