Ψ-W1-T4: resolve drop targets per move, not once — every surface gets a defined outcome, a cue, and no silent no-op

src/shell/actions/arrange_drop_win.h

@@ -0,0 +1,30 @@
+#pragma once
+// arrange_drop_win — the arrange outcome of the panel's drag-out gesture: places the dragged
+// bank captures on the timeline at the track and time under the pointer.
+//
+// LOAD-BEARING: this is USER-INITIATED PLACEMENT, the same class of act as RunInsertSelected.
+// Root CLAUDE.md's "capture and placement are separate acts" forbids a CAPTURE placing an item;
+// a deliberate drop onto the timeline is placement on demand, and the user chose the spot.
+// Nothing here captures or writes the bank.
+
+#include <string>
+#include <vector>
+
+// Declared as a class (matching reaper_plugin.h) so the mangled name agrees, without pulling
+// in the SDK.
+class MediaTrack;
+
+namespace reasampler {
+
+// The arrange time under a screen X, via REAPER's own pixel-column -> time mapping. Times left
+// of project start clamp to 0.
+double arrangeTimeAtScreenX(int screenX);
+
+// Places every path in `absolutePaths` on `track`, the first at `time` and each subsequent one
+// after the previous (REAPER's own multi-file drop shape), inside ONE undo block. The drop time
+// honors the project's snap setting. The caller's track selection and edit-cursor position are
+// restored before returning. Returns the number of files handed to REAPER.
+int performArrangeDrop(MediaTrack* track, double time,
+                       const std::vector<std::string>& absolutePaths);
+
+}  // namespace reasampler