feat: native host bridge integration — C++ bridge, Rust SHM, JS routing, build scripts, docs

- native_bridge/: InstrumentEngineManager multi-channel, sample-accurate, CC/program/pitchbend, transport, Vst3Instrument stub (HAVE_VST3SDK)
- src-tauri: shm.rs, bridge spawn + audio pump + health monitor, open_vst_gui, externalBin, commands
- app: UnifiedMidiRouter, NativeBridgeService, bridgeAudioNode, audioRoutingEngine, Plugin Manager UI, Bridge/WASM indicator, set_position sync
- build: 3 ps1 (force-added, build/ ignored), verify_bundle --check-bridge, CI workflow
- docs: TASKS.md, TEST_NOTES.md (Windows verify checklist), install/report updates

native_bridge/tests/shm_selfcheck.cpp

@@ -0,0 +1,67 @@
+// native_bridge/tests/shm_selfcheck.cpp
+// Self-check for SharedMemoryIPC helpers (assert-based, no framework).
+// POSIX path runs on Linux/macOS; Win32 path guarded (runs on Windows build).
+#include "../include/SharedMemoryIPC.h"
+#include "../src/SharedMemoryIPC.cpp"
+
+#include <cassert>
+#include <cstdio>
+#include <cstring>
+
+int main() {
+    // Use a test-only name to avoid clashing with a live DAW bridge.
+    ShmHandle* h = shm_open("SonicForge_SelfCheck_IPC");
+    assert(h != nullptr);
+
+    SharedAudioBufferIPC* ipc = shm_ptr(h);
+    assert(ipc != nullptr);
+    // Reset state (POSIX shm may survive an aborted previous run).
+    std::memset(ipc, 0, sizeof(SharedAudioBufferIPC));
+
+    // 1. MIDI event write + read back (A12: data2/data3 for CC/program/pitch bend)
+    assert(shm_write_midi(h, 0x9, 2, 60, 100, 37));
+    assert(ipc->midiQueueCount == 1);
+    assert(ipc->midiQueue[0].command == 0x9);
+    assert(ipc->midiQueue[0].channel == 2);
+    assert(ipc->midiQueue[0].pitch == 60);
+    assert(ipc->midiQueue[0].velocity == 100);
+    assert(ipc->midiQueue[0].sampleOffset == 37);
+    assert(ipc->midiQueue[0].data2 == 0 && ipc->midiQueue[0].data3 == 0);
+    assert(shm_write_midi(h, 0xB, 3, 64, 0, 0, 127));  // CC64 sustain = 127
+    assert(shm_write_midi(h, 0xE, 3, 0, 0, 0, 0x00, 0x40)); // pitch bend MSB
+    assert(ipc->midiQueue[1].data2 == 127);
+    assert(ipc->midiQueue[2].data3 == 0x40);
+    assert(ipc->midiQueueCount == 3);
+
+    // 2. Control event with path + channel (A10)
+    assert(shm_write_control(h, 2, 1 /*SOUNDFONT_SF2_SF3*/, 0, 4, "C:\\sf\\SGM.sf2"));
+    assert(ipc->controlQueueCount == 1);
+    assert(ipc->controlQueue[0].type == 2);
+    assert(ipc->controlQueue[0].arg0 == 1);
+    assert(ipc->controlQueue[0].channel == 4);
+    assert(std::strcmp(ipc->controlQueue[0].arg2, "C:\\sf\\SGM.sf2") == 0);
+    // TRANSPORT (A13): STOP with playhead arg
+    assert(shm_write_control(h, 3, 0, 44100, 0, ""));
+    assert(ipc->controlQueue[1].type == 3 && ipc->controlQueue[1].arg0 == 0
+           && ipc->controlQueue[1].arg1 == 44100);
+
+    // 3. Queue capacity guard
+    for (int i = 0; i < 70; ++i) shm_write_midi(h, 0x8, 0, 40, 0, 0);
+    assert(ipc->midiQueueCount == 64); // capped, not overflowed
+
+    // 4. Audio block round-trip
+    for (uint32_t i = 0; i < AUDIO_BLOCK_SIZE; ++i) ipc->masterLeft[i] = (float)i;
+    ipc->bridgeWriteIndex++;
+    ipc->blockTimestamp = 123456;
+    assert(ipc->masterLeft[255] == 255.0f);
+    assert(ipc->bridgeWriteIndex == 1);
+    assert(ipc->blockTimestamp == 123456);
+
+    // 5. Layout stability — MUST match Rust src-tauri/src/shm.rs
+    assert(sizeof(SharedAudioBufferIPC::MidiEventIPC) == 12);
+    assert(sizeof(SharedAudioBufferIPC::ControlEventIPC) == 1040);
+
+    std::printf("SHM self-check OK (sizeof struct = %zu bytes)\n", sizeof(SharedAudioBufferIPC));
+    shm_close(h);
+    return 0;
+}