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/actions.h

@@ -79,6 +79,14 @@ int bankPruneCommandId();
 // must invoke this ONLY after a successful/effective mutation — rejected ops (duplicate
 // name, un-deletable pool, etc.) must return before reaching here so no empty undo
 // point is ever opened for a no-op. Defined in actions.cpp alongside persistBook().
-void persistBankOp(const char* label);
+//
+// S9 bank-generation bump: pass `bumpGeneration = true` for a verb that changes what a live
+// instance would PLAY — move / copy / remove / evacuate / delete-with-members (a sample left,
+// arrived, or dropped out of a bank an instance may reference). Leave it false (the default)
+// for a PURELY ORGANIZATIONAL verb — create / rename / activate / reorder — which changes no
+// existing (bankId, sampleId) -> content mapping, so no instance need refresh. The bump (when
+// requested) happens INSIDE the block, BEFORE persistBook(), so the stamped counter rides the
+// same ext-state write and undo captures the pre/post generation with the rest of the blob.
+void persistBankOp(const char* label, bool bumpGeneration = false);
 
 }  // namespace reasampler