fix(vst): pin output bus to stereo (mode is decode-only) killing the hard-right pan; auto-default channel mode from the loaded capture (state v9)

tests/test_sample_map.cpp

@@ -129,6 +129,23 @@ static void testSelectNoLoopIsAbsent() {
     CHECK(sel && !sel->loop.hasLoop);  // absent loop -> hasLoop false (not a zero loop)
 }
 
+static void testSelectChannelCountThreaded() {
+    // GA: the bank's capture channel-count intrinsic rides SelectedSample so the shell can
+    // auto-default the channel mode (stereo capture -> Stereo). An entry without the
+    // intrinsic yields 0 (unknown — the auto-default skips it).
+    Sample st = makeSample("st", "Wide", "reasampler_bank/st.wav", 60);
+    st.channelCount = 2;
+    Sample mo = makeSample("mo", "Narrow", "reasampler_bank/mo.wav", 60);
+    mo.channelCount = 1;
+    const std::string json = bookJson({st, mo, makeSample("un", "Old", "reasampler_bank/un.wav", 60)}, {});
+    auto selSt = selectSample(json, "st");
+    CHECK(selSt && selSt->channelCount == 2);
+    auto selMo = selectSample(json, "mo");
+    CHECK(selMo && selMo->channelCount == 1);
+    auto selUn = selectSample(json, "un");
+    CHECK(selUn && selUn->channelCount == 0);  // unstamped -> unknown, never a guess
+}
+
 static void testSelectEmptyBlob() {
     CHECK(!selectSample("", "a").has_value());
 }
@@ -1320,6 +1337,55 @@ static void testComponentStateV8TruncatedMasterGain() {
     CHECK(back.selectionId.empty() && back.map.zones.empty());
 }
 
+// --- v9 component state: the GA channel-mode explicit flag ------------------------------------
+
+static void testComponentStateChannelModeExplicitRoundTrip() {
+    // The explicit flag survives a round-trip in BOTH states, its envelope neighbours intact.
+    ComponentState s;
+    s.selectionId = "pick";
+    s.channelMode = ChannelMode::Stereo;
+    s.channelModeExplicit = true;
+    s.masterGainLinear = 0.5;
+    ComponentState back = deserializeComponentState(serializeComponentState(s), 44100.0);
+    CHECK(back.channelModeExplicit);
+    CHECK(back.channelMode == ChannelMode::Stereo);
+    CHECK(std::fabs(back.masterGainLinear - 0.5) < 1e-12);
+    CHECK(back.selectionId == "pick");
+    s.channelModeExplicit = false;
+    back = deserializeComponentState(serializeComponentState(s), 44100.0);
+    CHECK(!back.channelModeExplicit);  // implicit round-trips too (not defaulted-true)
+    CHECK(back.channelMode == ChannelMode::Stereo);
+}
+
+static void testComponentStateV8LiftsImplicitChannelMode() {
+    // A GENUINE v8 blob (version tag 8: mode, marker, velocity, voice bytes, gain, id, zones —
+    // NO explicit flag) lifts to channelModeExplicit = FALSE: a pre-GA mode byte is treated as
+    // the un-touched default so the shell's auto-default may follow the loaded capture. Hand-
+    // built (serializeComponentState now emits v9, so it cannot make a v8 blob).
+    std::vector<std::uint8_t> v8;
+    v8.push_back(8); v8.push_back(0); v8.push_back(0); v8.push_back(0);    // version 8
+    v8.push_back(0);                                                        // channel mode = mono
+    for (int i = 0; i < 8; ++i) v8.push_back(0);                           // marker = 0
+    v8.push_back(88);                                                       // preview velocity
+    v8.push_back(7);                                                        // voice count
+    v8.push_back(0);                                                        // voice mode = poly
+    v8.push_back(0);                                                        // trigger = retrigger
+    for (int i = 0; i < 8; ++i) v8.push_back(0);                           // gain double bytes...
+    v8[17 + 6] = 0xF0; v8[17 + 7] = 0x3F;                                  // ...= 1.0 (LE IEEE-754)
+    const std::string id = "saved";
+    v8.push_back(static_cast<std::uint8_t>(id.size())); v8.push_back(0); v8.push_back(0); v8.push_back(0);
+    v8.insert(v8.end(), id.begin(), id.end());
+    v8.push_back(0); v8.push_back(0); v8.push_back(0); v8.push_back(0);    // zone count 0
+    const ComponentState back = deserializeComponentState(v8, 44100.0);
+    CHECK(!back.channelModeExplicit);  // pre-GA blob -> implicit (auto-default allowed)
+    CHECK(back.channelMode == ChannelMode::Mono);
+    CHECK(back.masterGainLinear == 1.0);
+    CHECK(back.previewVelocity == 88);
+    CHECK(back.voiceCount == 7);
+    CHECK(back.selectionId == "saved");
+    CHECK(back.map.zones.empty());
+}
+
 // --- MERGE COMPOSITION (S9 v5 marker envelope x S15/S16 v3 play-param payload) ----------------
 //
 // The merge of ps-w9-t1-sync (envelope v5, adds the consumed-assignment marker) and
@@ -2033,6 +2099,7 @@ int main() {
     testSelectRootNoteDefault();
     testSelectLoopThreaded();
     testSelectNoLoopIsAbsent();
+    testSelectChannelCountThreaded();
     testSelectEmptyBlob();
     testSelectMalformedBlob();
     testSelectZeroSamples();
@@ -2136,6 +2203,8 @@ int main() {
     testComponentStateV7LiftsUnityMasterGain();
     testComponentStateV8CorruptMasterGainFallsBack();
     testComponentStateV8TruncatedMasterGain();
+    testComponentStateChannelModeExplicitRoundTrip();
+    testComponentStateV8LiftsImplicitChannelMode();
     testV5EnvelopeWithMarkerAndPlayParamsRoundTrip();
     testV4BlobWithPlayParamsLiftsMarkerZeroKeepsPlay();
     testReconcileKeepsOnlySelectedFullRangeZone();