Decouple the instrument reload from VST3 activation, and make the master meter's accumulate exact

docs/TODO.md

@@ -240,57 +240,33 @@ alpha and this entry is re-filed against the new value.
 
 **Nothing here is actionable as a TODO.** Delete this entry when Γ-W1-T1 lands.
 
-## Decouple the instrument reload from VST3 activation
+## The editor's drag state machine has no seam, and `reasampler_editor.h` is near the ceiling
 
-**Context (Daniel, 2026-08-01 — Phase Γ fork Γ-F6, ruled closed).** Γ-W1-T2 ships the plugin's
-first latency reporting: `getLatencySamples()` returns 0 with the limiter off and the lookahead
-with it on, and the toggle calls `IComponentHandler::restartComponent(kLatencyChanged)`. The
-vendored SDK defines that flag as a host **deactivate/reactivate**
-(`pluginterfaces/vst/ivsteditcontroller.h:105-108`). **Dynamic latency reporting is routine for
-VST3 instruments and REAPER handles it as a matter of course** — the deactivate/reactivate is
-the normal contract, and for a typical plugin `setActive` only allocates and frees buffers.
-Γ-F6 was originally posed as "is this SDK cost acceptable?"; Daniel's answer relocated it:
-*"you have to have missed something, I used plenty of VST3s inside of REAPER that report PDC
-dynamically... Toggling the limiter killing the voices isn't a deal breaker though, the limiter
-will either be on or off on its instance, toggling during playback is not a use case."*
+**Context (Γ-W3, meter re-review).** `reasampler_editor.h` stands at **563 lines** against the
+~600-line ceiling — 37 lines of margin — and it keeps growing because every new surface on the
+Sample face adds its transient state there. The obvious seam is the drag state machine: `drag_`
+plus the per-gesture anchors it is read against.
 
-**The wart — and it is ours, not the SDK's.** `ReaSamplerProcessor::setActive(true)` calls
-`reloadInstrument()` (`src/shell/instrument/reasampler_processor.cpp:89-97`) — a bridge read
-plus a **full WAV re-decode** plus a fresh engine. `setActive(false)` frees `live_`,
-`draining_` and the graveyard (`:98-107`). So every host-driven activation cycle — a
-latency-change restart, an offline-render bracket, any host that deactivates around transport
-state — pays a disk read and a decode that nothing about activation requires. **Activation
-currently means two things at once**: "the audio thread may run" and "the decoded `SampleData`
-is (re)built." Dynamic latency is simply the first feature that makes the cycle
-user-triggerable.
+**Why it was declined rather than taken.** `drag_` has **42 references across 13 shell TUs**
+(measured over `src/shell/instrument/*.cpp`; the declaration in the header is additional), and
+every input TU both writes it and branches on it. Extracting it is a real refactor of the
+editor's input half, not a header move — and doing it inside a wave whose subject is the MASTER
+deck would have put an unrelated high-blast-radius change in the same diff. Declining was right;
+leaving it unrecorded was not.
 
-**Intended fix.** Separate the two lifetimes: keep the decoded `SampleData` alive across a
-deactivate and rebuild only the voice state on reactivate. The mechanism already exists in this
-file — `rebuildVoiceEngine` performs exactly that shape (drain-slot swap around the
-already-decoded `SampleData`, no bank re-read, no WAV re-decode) for voice-count and voice-mode
-edits. This is a lifetime split, not a new mechanism.
+**The shape a fix would take.** A `DragState` type owning the kind plus its anchor payload,
+with the input TUs mutating it through named transitions rather than assigning `drag_` and its
+anchors independently — which is also what would let the invariant "an anchor is only readable
+while its own `DragKind` is in flight" be enforced rather than observed. `editor_interaction.h`
+already holds the `DragKind` vocabulary and is the natural home.
 
-**The constraint the fix MUST handle.** The deactivate's destruction is deliberate and its
-reason is documented at the call site: a surviving `live_` would be displaced into the drain
-slot on reactivate and *"resurrect stale sustained voices as ghosts."* **Voice state must still
-die across the cycle** — only the decoded PCM survives, and those are two different lifetimes
-currently collapsed into one. Second constraint: `setActive(true)` is also the non-editor
-legacy-lift trigger for a pre-v10 blob (its opportunistic `refreshRefsFromBank` copies refs in
-once the bank blob is readable), so a path that skips the bridge read must keep that lift
-reachable — the comment at `:90-96` records the residual load-order race it exists to cover.
+**Priority / risk.** Low, but the margin is the clock: the next surface that adds two members to
+the header takes it over the ceiling, and at that point the seam gets chosen under time pressure
+by whoever is unlucky. Take it before that, not after.
 
-**Priority / risk.** Low; deferred by ruling. Nothing is incorrect today, only wasteful, and
-Daniel has explicitly accepted the user-visible consequence (held notes cut on a limiter
-toggle). **Trigger conditions — revisit when any one of these holds:** (a) a second
-latency-changing control appears, so the cycle stops being a once-per-patch event; (b) the
-limiter enable is ever wanted automatable, which `docs/product/parameter-automation.md` §3.8
-currently forbids *because* of this cost; or (c) the re-decode is observed to be perceptible in
-REAPER — Γ-W1-T2's review records that observation for exactly this purpose.
-
-**Done looks like.** A host-driven deactivate/reactivate cycle costs no disk I/O and no WAV
-decode; sounding voices are still destroyed across it, with no ghost-resurrection regression;
-a pre-v10 blob still lifts; and `getLatencySamples()` still derives from persisted state rather
-than from a transient the deactivate cleared.
+**Done looks like.** `reasampler_editor.h` is back under the ceiling with room; no TU assigns
+`drag_` and an anchor as two independent writes; and the transitions are named where the
+`DragKind` catalogue already lives.
 
 ## `Sample::sourceMode` has no value meaning "produced by the instrument"