Fix embed use-after-free, restore golden fixture + refs tests, drop dead note_entry

src/shell/instrument/CLAUDE.md

@@ -10,7 +10,7 @@ two small identity/helper headers this directory owns outright
 The pure engine/geometry core this shell wraps (`sampler_core`, `pitch_shift`,
 `sample_map`, `component_state_io`, `play_params.h`, `editor_geometry`, `sample_bands`,
 `sample_chrome`, `keyboard_strip`, `waveform_view`, `capture_browser`, `browser_scroll`,
-`note_entry`, `param_slider`, `trigger_seam`, `velocity_curve`, `embed_strip`, `knob_deck`,
+`param_slider`, `trigger_seam`, `velocity_curve`, `embed_strip`, `knob_deck`,
 `curve_popup`, `master_gain`, `reasampler_uid.h`) lives in `core/instrument/*` and
 `core/wire` and is documented there — this directory consumes it but does not own it.
 

src/shell/instrument/processor_reload.cpp

@@ -232,7 +232,7 @@ void ReaSamplerProcessor::publishBuiltLocked(std::unique_ptr<LoadedInstrument> b
 
 void ReaSamplerProcessor::rebuildVoiceEngine() {
     // Off the audio thread. A voice-param change touches no audio data, so this rebuilds
-    // the engine around a copy of the live instrument's already-decoded keymap — no
+    // the engine around a copy of the live instrument's already-decoded SampleData — no
     // bridge, no disk — and publishes through the same drain-slot swap.
     std::lock_guard<std::mutex> lock(reloadMutex_);
     LoadedInstrument* cur = live_.load(std::memory_order_acquire);

src/shell/instrument/reasampler_embed.cpp

@@ -78,10 +78,13 @@ void ReaSamplerEmbed::refreshLoaded() {
     const InstrumentParams params = processor_->instrumentParams();
     if (params.rootOverride) {
         rootNote_ = *params.rootOverride;
-    } else if (const SelectedSample* ref = findRef(processor_->sampleRefs(), loadedId_)) {
-        rootNote_ = ref->rootNote;
     } else {
-        rootNote_ = 60;
+        const SampleRefs refs = processor_->sampleRefs();
+        if (const SelectedSample* ref = findRef(refs, loadedId_)) {
+            rootNote_ = ref->rootNote;
+        } else {
+            rootNote_ = 60;
+        }
     }
 }
 

src/shell/instrument/reasampler_processor.h

@@ -165,8 +165,8 @@ public:
     void setPreviewVelocity(std::uint8_t velocity);
 
     // Voice-system parameters (per-instance), guarded by voiceParamsMutex_, not read on the
-    // audio thread — each setter rebuilds via rebuildVoiceEngine (already-decoded keymap, no
-    // bridge/WAV re-read) through the same drain-slot swap, so a change never cuts a tail.
+    // audio thread — each setter rebuilds via rebuildVoiceEngine (already-decoded SampleData,
+    // no bridge/WAV re-read) through the same drain-slot swap, so a change never cuts a tail.
     int voiceCount();
     void setVoiceCount(int count);        // clamped to kMinVoiceCount..kMaxVoiceCount
     VoiceMode voiceMode();