fix(ingest): convert-on-import to 32f WAV, undo-group bank+assign, overflow guards

Non-WAV sources decode via PCM_source::GetSamples and land as canonical 32f
RIFF/WAVE; hash taken post-conversion so re-imports dedup. Undo block covers
bank mutation + assign_request atomically. Overflow guards + adversarial tests.

src/main.cpp

@@ -867,15 +867,34 @@ static std::string RunCapture(const reasampler::CaptureActionDef& def)
 // inserts a timeline item (load-bearing principle); the only addition here is the
 // bank-index-id -> assignment-request write after the sample lands. If the capture
 // failed / no-op'd (empty id), no assignment is written (nothing to assign).
+//
+// UNDO GROUPING: both the bank mutation (RunCapture -> saveToActiveProject) AND the
+// assignment-request write (ingestAssignActiveInstance -> writeAssignmentRequest) are
+// wrapped in a single undo block so Ctrl-Z rolls back both ext-state keys atomically.
+// An undo that removes the captured sample also clears the assign_request that named it,
+// preventing a stale request from pointing at a removed sample. The block uses the house
+// pattern (UNDO_STATE_MISCCFG, discarded on an unsaved project with empty label + zero
+// flag) matching the bank-op family in actions.cpp.
 static void RunCaptureItemAssign()
 {
     // Reuse the Item-scope def from the capture table (index 0) — same range logic, same
     // FX-scope neutralize, same bank/persist landing as the plain "capture item" action.
+    Undo_BeginBlock2(nullptr);
+
     const std::string sampleId =
         RunCapture(reasampler::captureActionTable()[0]);
-    if (sampleId.empty()) return;  // capture failed / no-op — RunCapture already reported
+    if (sampleId.empty())
+    {
+        // Capture failed or no-op'd — RunCapture already reported. Discard the empty point.
+        Undo_EndBlock2(nullptr, "", 0);
+        return;
+    }
 
+    // Assign inside the same block so undo clears both keys together.
     reasampler::ingestAssignActiveInstance(g_session.book().activeBankId(), sampleId);
+    Undo_EndBlock2(nullptr, "ReaSampler: capture + assign to active instance",
+                   UNDO_STATE_MISCCFG);
+
     reasampler::bankPanelRefresh();
     ShowConsoleMsg("ReaSampler ingest: captured into the bank and assigned to the active "
                    "instance.\n");