Q-W1 pt2: core/shell/app relocation + sub-namespaces; one concrete ui::Rect (LTRB fork retired); slot_map split from bank_book; BankIndex→BankModel; 59/59 green

src/shell/actions/drag_out_win.h

@@ -0,0 +1,44 @@
+#include "core/namespaces.h"
+#pragma once
+// drag_out_win — the OS/COM initiation half of native OS drag-out (Milestone 11). The pure
+// gesture-boundary decision and path-list assembly live in drag_out.*; THIS is the platform
+// shell that hands a resolved, existing-file path list to the operating system's drag-drop
+// machinery so the user can drop bank samples into Explorer / another app / another DAW.
+//
+// ONE seam, platform-forked inside the .cpp:
+//   * Windows (primary — Daniel's target): OLE DoDragDrop with a minimal IDataObject
+//     carrying CF_HDROP (absolute paths, double-null-terminated wide list) and a minimal
+//     IDropSource. COPY-ONLY is STRUCTURAL: the IDataObject offers DROPEFFECT_COPY and the
+//     effect mask passed to DoDragDrop is DROPEFFECT_COPY alone — MOVE is never offered, so
+//     no target can pull the bank file out of the bank folder (invariant #1: a move would
+//     delete bank bytes, and per the Phase R boundary ONLY prune deletes files).
+//   * macOS/Linux (SWELL): SWELL_InitiateDragDropOfFileList (verified present in
+//     vendor/WDL/WDL/swell/swell-functions.h) behind the same seam. SWELL's file-list drag
+//     is a copy-style file drag; it exposes no per-source effect mask the way OLE does, so
+//     the copy-only guarantee there rests on SWELL's copy semantics rather than an explicit
+//     mask — noted honestly, not faked. Windows is where the mask control is exact.
+//
+// NON-DESTRUCTIVE (invariant #2): initiating a drag reads nothing but the path list and
+// mutates no sample / index / selection. A cancelled or failed drag changes nothing — the
+// OS layer here neither writes ext-state nor touches the book.
+
+#include <string>
+#include <vector>
+
+struct HWND__;  // avoid dragging windows.h into every includer; the shell casts as needed.
+
+namespace reasampler {
+
+// Initiates a native OS drag-out of `absolutePaths` (already resolved, existing, de-duped —
+// the pure drag_out::assemblePathList output) from the panel window `panelHwnd`. COPY-ONLY;
+// see the header note. A no-op when the path list is empty (nothing draggable — the caller
+// checks this too, but the guard is repeated here so a direct call is safe).
+//
+// BLOCKING on Windows: OLE DoDragDrop runs its own modal message loop until the drop or
+// cancel, then returns — the caller's gesture state should be reset AFTER this returns.
+// Returns true if a drop was accepted (DROPEFFECT_COPY), false on cancel / failure /
+// empty input. The return is advisory (a failed drag is visible by nothing happening —
+// the caller does not surface an error, per the brief's no-console-output constraint).
+bool initiateDragOut(HWND__* panelHwnd, const std::vector<std::string>& absolutePaths);
+
+} // namespace reasampler