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/ingest.cpp

@@ -458,6 +458,10 @@ void doImportFromMediaExplorer() {
     // zero flag so REAPER discards the undo entry (the house pattern from actions.cpp).
     if (r.added) {
         Undo_BeginBlock2(nullptr);
+        // S9: an ingest import adds a sample to the active bank -> bump inside the block so
+        // the stamped generation refreshes the assigned instance hands-free (and undo rolls
+        // the generation back with the banks/assign_request keys).
+        g_session->bumpBankGeneration();
         const bool persisted = g_session->saveToActiveProject();
         // Assign request inside the same block: undo rolls back both keys together.
         ingestAssignActiveInstance(g_session->book().activeBankId(), r.sampleId);
@@ -531,6 +535,9 @@ void ingestDroppedFiles(const std::vector<std::string>& absolutePaths) {
     if (!firstAssignId.empty()) {
         if (importedNew > 0) {
             Undo_BeginBlock2(nullptr);
+            // S9: one coalesced bump for the whole drop (>=1 new sample landed) inside the
+            // block so the generation refreshes the assigned instance and undo rolls it back.
+            g_session->bumpBankGeneration();
             const bool persisted = g_session->saveToActiveProject();
             // Assign inside the block: undo restores both keys atomically.
             ingestAssignActiveInstance(firstAssignBank, firstAssignId);