Merge pS-ga-stereo: pin stereo bus (kills dual-mono hard-right pan) + auto-default channel mode from capture (v9)

src/instrument_drop.cpp

@@ -76,10 +76,11 @@ std::vector<std::uint8_t> buildVstPresetBytes(
 
 std::vector<std::uint8_t> instrumentDropStateBytes(const std::string& sampleId) {
     // The ONE fact the drop carries: this capture is the instance's selection. Everything
-    // else stays at the fresh-instance defaults (no zones, mono, generation 0) — the same
-    // ComponentState a browser click would produce. serializeComponentState is the
-    // instrument's own writer (the single source of truth for the byte layout), so this is
-    // NOT a parallel encoder — it IS the instrument's encoder.
+    // else stays at the fresh-instance defaults (no zones, implicit channel mode, generation
+    // 0) — the same ComponentState a browser click would produce. The implicit mode means
+    // the GA auto-default will follow the loaded capture's channel count on first reload.
+    // serializeComponentState is the instrument's own writer (the single source of truth for
+    // the byte layout), so this is NOT a parallel encoder — it IS the instrument's encoder.
     ComponentState cs;
     cs.selectionId = sampleId;
     return serializeComponentState(cs);