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.

tests/test_sample_map.cpp

@@ -979,6 +979,58 @@ static void testComponentStateV4StereoWithZoneOverridesRoundTrip() {
           !back.map.zones[1].startPoint.has_value());
 }
 
+// --- v5 component state: the S8/S9 last-consumed-assignment marker -------------
+
+static void testComponentStateV5MarkerRoundTrip() {
+    // The consumed-assignment generation (S8 reader marker) round-trips through the v5 envelope
+    // alongside selection + mode + zones. A non-zero, > 32-bit value proves the 8-byte LE field.
+    ComponentState s;
+    s.selectionId = "pick";
+    s.channelMode = ChannelMode::Stereo;
+    s.lastConsumedAssignGeneration = 1700000123456LL;  // > INT32_MAX
+    s.map.zones.push_back(zone("z0", 0, 127, /*override=*/std::nullopt));
+    const ComponentState back = deserializeComponentState(serializeComponentState(s));
+    CHECK(back.lastConsumedAssignGeneration == 1700000123456LL);  // marker survives
+    CHECK(back.channelMode == ChannelMode::Stereo);
+    CHECK(back.selectionId == "pick");
+    CHECK(back.map.zones.size() == 1 && back.map.zones[0].sampleId == "z0");
+}
+
+static void testComponentStateDefaultMarkerIsZero() {
+    // A default-constructed state has marker 0 and round-trips 0 — a fresh instance's first
+    // assign (generation >= 1) must not be swallowed by a non-zero default.
+    const ComponentState back = deserializeComponentState(serializeComponentState(ComponentState{}));
+    CHECK(back.lastConsumedAssignGeneration == 0);
+}
+
+static void testComponentStateV4LiftsMarkerToZero() {
+    // A GENUINE v4 blob (version tag 4: mode byte, then id + zones — NO 8-byte marker) must lift
+    // with lastConsumedAssignGeneration = 0 and its mode/selection/zones intact. Build it by hand
+    // (serializeComponentState now emits v5, so we cannot use it to make a v4 blob). This proves
+    // an already-saved pre-S8/S9 instance restores cleanly and its first assign still applies.
+    std::vector<std::uint8_t> v4;
+    v4.push_back(4); v4.push_back(0); v4.push_back(0); v4.push_back(0);   // version 4
+    v4.push_back(1);                                                       // channel mode = stereo
+    const std::string id = "saved";
+    v4.push_back(static_cast<std::uint8_t>(id.size())); v4.push_back(0); v4.push_back(0); v4.push_back(0);
+    v4.insert(v4.end(), id.begin(), id.end());
+    v4.push_back(0); v4.push_back(0); v4.push_back(0); v4.push_back(0);   // zone count 0
+    const ComponentState back = deserializeComponentState(v4);
+    CHECK(back.lastConsumedAssignGeneration == 0);         // no marker in v4 -> default 0
+    CHECK(back.channelMode == ChannelMode::Stereo);        // v4 mode byte still honored
+    CHECK(back.selectionId == "saved");
+    CHECK(back.map.zones.empty());
+}
+
+static void testComponentStateV5TruncatedMarker() {
+    // A v5 blob truncated inside the 8-byte marker (mode byte present, marker cut short) -> empty,
+    // mono + marker 0 default holds (bounded read, never throws across the host).
+    std::vector<std::uint8_t> t{5, 0, 0, 0, 1, 0xAA, 0xBB};  // version 5, mode byte, 2 marker bytes
+    const ComponentState back = deserializeComponentState(t);
+    CHECK(back.lastConsumedAssignGeneration == 0);
+    CHECK(back.selectionId.empty() && back.map.zones.empty());
+}
+
 int main() {
     testSelectByIdHit();
     testSelectEmptyIdIsSilence();
@@ -1049,6 +1101,10 @@ int main() {
     testComponentStateV1V2LiftToMono();
     testComponentStateV4TruncatedModeByte();
     testComponentStateV4StereoWithZoneOverridesRoundTrip();
+    testComponentStateV5MarkerRoundTrip();
+    testComponentStateDefaultMarkerIsZero();
+    testComponentStateV4LiftsMarkerToZero();
+    testComponentStateV5TruncatedMarker();
 
     if (g_fail == 0) std::printf("sample_map: all tests passed\n");
     return g_fail != 0;