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_editor.h

@@ -88,6 +88,15 @@ private:
     void onMouseMove(int x, int y);
     void onMouseUp(int x, int y);
 
+    // The S9/S8 change-detection tick (WM_TIMER on the child window — the UI thread, NEVER the
+    // audio thread). Polls the processor's bank-sync (generation change -> hands-free reload;
+    // a new assignment request -> apply as this instance's selection) and, when anything
+    // changed, re-snapshots the editor's own view (refreshFromBank) + repaints so the browser /
+    // setup surface reflect the new bank. An open editor means THIS instance is the focused
+    // assignment target (the thundering-herd policy — see the handoff), so it passes true.
+    // Suppressed WHILE A DRAG IS IN FLIGHT so a mid-drag reload does not yank the edit surface.
+    void onSyncTimer();
+
     static LRESULT CALLBACK wndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
     void invalidate();