Fix drag-out losing audio and FX-container drops losing the capture; re-home ingest under shell/actions

tests/test_instrument_drop.cpp

@@ -234,6 +234,72 @@ static void testEmbedStripIsNotHotspot() {
     CHECK(!infoNamesFxHotspot("mcp.fxembed extra"));
 }
 
+// --- Drop surface parity: container vs FX button ------------------------------
+//
+// The container-drop regression (instance loads, capture does not): the two surfaces must be
+// one code path carrying one payload. The payload is a function of the capture alone, so the
+// surface cannot influence it — and both surfaces must classify as hotspots so both reach it.
+
+// Every surface a drop can land on admits the SAME capture and yields a payload that decodes
+// back to it. The payload takes the capture and nothing else, so the surface cannot influence
+// it — walking the surfaces here is what pins that the container family is not second-class.
+static void testEveryDropSurfaceCarriesTheCapture() {
+    const char* surfaces[] = {
+        "fx_chain",  // FX chain window / container list — the reported failing surface
+        "fx_0",      // floating FX window
+        "tcp.fx",    // TCP FX button — the reference path
+        "mcp.fx",    // MCP FX button
+    };
+    const std::string sampleId = "cap-7f3a";
+    for (const char* info : surfaces) {
+        CHECK(infoNamesFxHotspot(info));
+        const ParsedPreset p = parsePreset(buildInstrumentDropPreset(sampleId));
+        CHECK(p.ok);
+        CHECK(p.classId == vstClassIdHex());
+        const ComponentState cs = deserializeComponentState(p.compChunk, kRate);
+        CHECK(cs.selectionId == sampleId);
+    }
+}
+
+// --- All-or-nothing rollback --------------------------------------------------
+
+// The add failed: nothing was created, so there is nothing to delete and nothing loaded.
+static void testAddFailureLeavesNothingToRollBack() {
+    const DropOutcome out = decideDropOutcome(DropAttempt{-1, false});
+    CHECK(!out.loaded);
+    CHECK(out.rollbackFxIndex < 0);
+}
+
+// The instance was created but the preset did not apply: the caller MUST delete that exact
+// index — an instance without its capture is the orphan the contract forbids.
+static void testPresetFailureRollsBackTheCreatedIndex() {
+    const DropOutcome zero = decideDropOutcome(DropAttempt{0, false});
+    CHECK(!zero.loaded);
+    CHECK(zero.rollbackFxIndex == 0);
+    const DropOutcome later = decideDropOutcome(DropAttempt{4, false});
+    CHECK(!later.loaded);
+    CHECK(later.rollbackFxIndex == 4);
+    // Container-addressed indices (0x2000000-flagged) roll back by the same rule — the
+    // obligation follows the index REAPER handed back, whatever space it names.
+    const DropOutcome inContainer = decideDropOutcome(DropAttempt{0x2000000 + 5, false});
+    CHECK(!inContainer.loaded);
+    CHECK(inContainer.rollbackFxIndex == 0x2000000 + 5);
+}
+
+// Both halves succeeded: loaded, and nothing to undo.
+static void testSuccessKeepsTheInstance() {
+    const DropOutcome out = decideDropOutcome(DropAttempt{2, true});
+    CHECK(out.loaded);
+    CHECK(out.rollbackFxIndex < 0);
+}
+
+// A "preset applied" report with no instance behind it can never read as loaded.
+static void testNoInstanceIsNeverLoaded() {
+    const DropOutcome out = decideDropOutcome(DropAttempt{-1, true});
+    CHECK(!out.loaded);
+    CHECK(out.rollbackFxIndex < 0);
+}
+
 int main() {
     testClassIdHexPinnedPerChannel();
     testPresetRoundTripsThroughInstrumentReader();
@@ -248,6 +314,12 @@ int main() {
     testNonFxSurfacesAreNotHotspot();
     testEmbedStripIsNotHotspot();
 
+    testEveryDropSurfaceCarriesTheCapture();
+    testAddFailureLeavesNothingToRollBack();
+    testPresetFailureRollsBackTheCreatedIndex();
+    testSuccessKeepsTheInstance();
+    testNoInstanceIsNeverLoaded();
+
     if (g_fail == 0) std::printf("All tests passed.\n");
     return g_fail ? 1 : 0;
 }