instrument: deliver continuous playback params live to sounding voices via a seqlock block, holding normalized stage position across time edits

src/shell/instrument/CLAUDE.md

@@ -67,6 +67,20 @@ scattered `#ifdef`s in the VST shell, except the one described below).
 - **Verify** all identity/factory wiring against the vendored Steinberg SDK
   (`DEF_CLASS2` / `INLINE_UID` / `FUID` from `pluginfactory.h` + `funknown.h`).
 
+**The three commit tiers (Θ-W3).** An edit reaches the audio by exactly one of three routes, and
+which route a control takes is decided once, by the pure `isLiveDeckParam` predicate — see
+`core/instrument/CLAUDE.md`'s "Live parameter delivery" for the rule and its rationale.
+1. **Full reload** — `reloadInstrument`: bridge read, WAV re-decode, fresh engine, snapshot swap.
+2. **Engine rebuild** — `rebuildVoiceEngine`: same drain-slot swap around the already-decoded
+   `SampleData`. Voice count / mode / mono trigger.
+3. **Live** — `publishLiveParams` (and `masterGain_`, the original of the shape): a lock-free
+   publish the audio thread observes at block boundaries. No rebuild, no snapshot, no disk.
+
+`liveParams_` is declared ahead of the instrument slots so it outlives every snapshot pointing at
+it. The editor's `commitLive` is the tier-3 peer of `commitAndReload` and still writes the
+parameter set, so persistence is unchanged — `getState` serializes `params_`, never a reload
+artifact, and the reload was never the persistence trigger.
+
 **Non-goals / guardrails.**
 - The instrument never captures and never inserts into the arrange. Playback is a
   read-only act over the bank. Any instrument path that captures, places a timeline