fix(instrument_drop): narrow FX hotspot to tcp.fx/mcp.fx, not bare tcp/mcp (S-VIEW-BUG-1)

src/instrument_drop_win.h

@@ -33,14 +33,14 @@ struct FxDropTarget {
 };
 
 // Hit-test a screen point (REAPER screen coords) to an FX drop target. Wraps
-// GetThingFromPoint, whose info string tells us what was hit ("tcp"/"mcp" for a track panel,
-// "fx_chain"/"fx_N" for the FX area/button). `overReaperUi` is the shell-supplied predicate
-// the pure drag_out::decideGesture consumes (true when the point is over REAPER's own UI —
-// i.e. GetThingFromPoint returned a track OR a recognizable non-track thing, false when the
-// pointer has left REAPER entirely). `overFxHotspot` is true when the info string names the
-// FX region specifically — the S17 "FX-button hotspot vs. whole TCP" question is resolved to
-// the FX hotspot (the discoverable, unambiguous target), decided here from the SDK's own
-// hit-test string rather than a home-grown geometry guess.
+// GetThingFromPoint, whose info string tells us what was hit ("tcp.fx"/"mcp.fx" for the TCP/MCP
+// FX button; "fx_chain"/"fx_N" for the FX-chain and floating-FX windows; bare "tcp"/"mcp" or
+// other "tcp.*"/"mcp.*" tokens for non-FX track-panel regions). `overReaperUi` is the
+// shell-supplied predicate the pure drag_out::decideGesture consumes (true when the point is
+// over REAPER's own UI — i.e. GetThingFromPoint returned a track OR a recognizable non-track
+// thing, false when the pointer has left REAPER entirely). `overFxHotspot` is true only when
+// the info string names a genuine FX-bearing surface ("tcp.fx", "mcp.fx", or "fx_*") —
+// decided by instrument_drop::infoNamesFxHotspot from the SDK's own hit-test string.
 FxDropTarget resolveFxDropTarget(int screenX, int screenY);
 
 // Perform the drop on `track`: add a fresh ReaSampler 9000 instance and inject `chunkBase64`