Drag&drop: Seed Move op at drag start to remove same-volume "+" flicker

Both `performSingleFileDrag` and `performSelectionDrag` now push `'move'` via `setSelfDragResolvedOperation` right before the native `startDrag`. So the very first `draggingEntered:` already returns Move and the OS draws no "+" badge for the same-volume case (the default and most common path).

For cross-volume drags the first `handleDragOver` flips the op to Copy, so the "+" appears ~5–30ms later. Picked this direction over the reverse because a badge appearing late feels intentional, while a badge appearing-then-disappearing reads as a glitch.

Updated the gotcha in `drag/CLAUDE.md` to describe the new behavior.

Author: vdavid

apps/desktop/src/lib/file-explorer/drag/CLAUDE.md

@@ -169,13 +169,13 @@ Key files:
     > 1 `NSDraggingItem`s on the pasteboard. Even when the OS image is swapped to transparent for self-drags, the badges
     > still draw because they're separate sprites near the cursor, not painted onto the image surface. Don't try to
     > replace or skin them — invest custom branding into `DragOverlay.svelte` instead, which is fully under our control.
-- **Gotcha**: The "+" badge may briefly flash on the first frame of a self-drag
-  - **Why**: Our swizzle overrides the wry-default `Copy` return only after the frontend has pushed a resolved op via
-    `setSelfDragResolvedOperation`. The very first `draggingEntered:` can run before that IPC lands, so macOS can show
-    "+" for a frame or two before flipping to the correct op on the next `draggingUpdated:`. Visible as a tiny flicker
-    on the very first drag start, not on subsequent updates. To eliminate it entirely we'd need to push an initial
-    "best-guess" op (likely `Move`, since same-volume default is Move) right before `startDrag`. Not done yet because
-    the flicker is nearly imperceptible in practice.
+- **Gotcha**: For cross-volume self-drags, the "+" badge may appear ~1–2 frames late
+  - **Why**: Both `performSingleFileDrag` and `performSelectionDrag` seed the swizzle with `'move'` via
+    `setSelfDragResolvedOperation` right before `startDrag`, so the same-volume case (the default, most common) shows no
+    "+" from frame one. For cross-volume drags the resolved op is `'copy'`, but JS only learns the target volume after
+    the first `handleDragOver`, so the badge flips from "no +" to "+" on the next `draggingUpdated:` — a slight "+"
+    appearing late, ~5–30ms. Picked this direction over the reverse because a badge appearing later feels intentional,
+    while a badge appearing-then-disappearing reads as a glitch.
 
 ## Platform support
 

apps/desktop/src/lib/file-explorer/drag/drag-drop.ts

@@ -18,7 +18,13 @@
 
 import { tempDir, join } from '@tauri-apps/api/path'
 import { getCachedIcon } from '$lib/icon-cache'
-import { startSelectionDrag, startDragPaths, prepareSelfDragOverlay, clearSelfDragOverlay } from '$lib/tauri-commands'
+import {
+  startSelectionDrag,
+  startDragPaths,
+  prepareSelfDragOverlay,
+  clearSelfDragOverlay,
+  setSelfDragResolvedOperation,
+} from '$lib/tauri-commands'
 import { getSetting } from '$lib/settings/settings-store'
 import { cancelClickToRename } from '../rename/rename-activation'
 import { renderDragImage } from './drag-image-renderer'
@@ -365,6 +371,13 @@ async function performSingleFileDrag(filePath: string, iconId: string, fileInfo?
   // Store rich image path so native swizzle can swap to it on window exit
   await prepareSelfDragOverlay(resolved.path)
 
+  // Seed the swizzle with our best-guess op so the very first draggingEntered:
+  // returns Move (no badge) instead of wry's hardcoded Copy ("+"). 'move' wins
+  // over 'copy' as the default because it's the same-volume case (most common)
+  // and because a "+" appearing later feels intentional, while a "+" disappearing
+  // would feel like a glitch.
+  await setSelfDragResolvedOperation('move')
+
   // Don't reset draggingFromSelf after the start call — it resolves before the
   // OS delivers drop/leave events. The flag is cleared by the drop handler.
   draggingFromSelf = true
@@ -386,6 +399,9 @@ async function performSelectionDrag(context: SelectionDragContext): Promise<void
   // Store rich image path so native swizzle can swap to it on window exit
   await prepareSelfDragOverlay(resolved.path)
 
+  // Seed the swizzle with our best-guess op — see performSingleFileDrag comment.
+  await setSelfDragResolvedOperation('move')
+
   // Don't reset draggingFromSelf after startDrag — see performSingleFileDrag comment.
   draggingFromSelf = true
   await startSelectionDrag(context.listingId, context.indices, context.includeHidden, context.hasParent, resolved.path)