feat(S9/S8): bank-generation change-detection + instrument-side assignment reader

Extension stamps a monotonic bank_generation counter, bumped at content
mutations; the VST3 instrument polls it off-thread on an editor timer and
consumes assignment requests, refreshing playback hands-free.

src/vst/reasampler_embed.h

@@ -32,6 +32,7 @@
 
 #pragma once
 
+#include <cstdint>
 #include <string>
 #include <vector>
 
@@ -86,7 +87,19 @@ private:
     // as the editor's refreshSampleList does (bridge read + processor accessors, UI thread).
     void refresh();
 
+    // The S9 dirty-guard over refresh() (the S6 flagged follow-up): read the cheap bank-
+    // generation stamp; do the EXPENSIVE bank-blob bridge read (refresh()) only when the
+    // generation changed since the last paint (or on the first paint) — the strip re-read
+    // per paint was wasteful now that a generation counter exists. The performance map (a
+    // cheap in-process accessor, edited by the editor independently of bank content) is
+    // ALWAYS refreshed so a zone edit still reflects immediately. UI thread only.
+    void maybeRefresh();
+
     ReaSamplerProcessor* processor_ = nullptr;
+    // The bank generation last folded into samples_ (S9 dirty-guard). -1 forces the first
+    // maybeRefresh() to do a full read (no generation can be negative — parseBankGeneration
+    // yields >= 0 — so -1 is an "unprimed" sentinel distinct from a real generation 0).
+    std::int64_t lastSeenBankGeneration_ = -1;
     // Snapshotted for the current paint (refreshed each paint off the audio thread).
     std::vector<SampleChoice> samples_;
     PerformanceMap map_;