Bugfix: File ops now process selection in pane order

- Copy/move/delete used to process selected items in Cmd+click order, not pane sort order, because `SvelteSet<number>` iteration preserves insertion. Cmd+clicking rows 15, 5, 10 sent paths to the backend as `[15, 5, 10]`; the backend faithfully copied them in that order, surprising users who expected top-to-bottom processing.
- `selection-state.svelte.ts::getSelectedIndices()` now sorts ascending before returning. Visible-index ascending = pane sort order (the listing cache is sorted at fetch time). The `SvelteSet` itself stays insertion-ordered; only the read-out is sorted. All five FE call sites (copy/move/delete/trash/clipboard) flow through this single helper.
- For SMB ≥3 files the volume-copy concurrent path's spawn order now matches pane order; completion races by design (`concurrency=8`).
- Added Vitest cases for ascending order after non-monotonic toggles and from non-sorted `setSelectedIndices` input.
- Updated `file-explorer/CLAUDE.md` § Selection / Implementation to document the visible-index-ascending guarantee.

Author: vdavid

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

@@ -36,6 +36,9 @@ Dual-pane file explorer with keyboard-driven navigation, file selection, sorting
 - **State**: `SvelteSet<number>` (from `svelte/reactivity`) in `FilePane.svelte`. O(1) add/remove/has
 - **Preserved on sort/filter**: `resort_listing` accepts `selectedIndices[]`, returns `newSelectedIndices[]`
 - **Write operations receive indices**: backend resolves to paths from cached listing
+- **Visible-index ascending order**: `selection-state.svelte.ts::getSelectedIndices()` sorts ascending before
+  returning, so write ops process selections top-to-bottom in pane sort order regardless of Cmd+click sequence. The
+  `SvelteSet` itself remains insertion-ordered; only the read-out for callers is sorted.
 - **Visual**: three-tier `--color-selection-fg` cascade (red, Total-Commander-style):
   - `--color-selection-fg-primary` (strong red — `#cc0000` light, `#ff4040` dark) applies on the selection bg.
   - `--color-selection-fg-cursor` (`#b80808` / `#ff8c8c`) takes over when the row is also under the cursor

apps/desktop/src/lib/file-explorer/pane/selection-state.svelte.ts

@@ -180,7 +180,11 @@ export function createSelectionState(options?: { onChanged?: () => void }) {
   }
 
   function getSelectedIndices(): number[] {
-    return Array.from(selectedIndices)
+    // Ascending visible-index order = pane sort order (the listing cache is
+    // sorted at fetch time). Write ops process this array top-to-bottom, so
+    // the user sees files copied/moved/deleted in the order they appear in
+    // the pane, regardless of the order they were Cmd+clicked in.
+    return Array.from(selectedIndices).sort((a, b) => a - b)
   }
 
   function setSelectedIndices(indices: number[]) {

apps/desktop/src/lib/file-explorer/pane/selection-state.test.ts

@@ -135,6 +135,24 @@ describe('createSelectionState', () => {
       state.setSelectedIndices([1])
       expect(onChanged).toHaveBeenCalled()
     })
+
+    it('returns indices in ascending order regardless of selection sequence', () => {
+      // Visible-index ascending is pane-sort order (the listing cache is sorted
+      // at fetch time). Write ops process this Vec top-to-bottom, so the user
+      // sees the same files copied/moved/deleted first as the ones at the top
+      // of the pane, even when they Cmd+clicked them in a non-monotonic order.
+      const state = createSelectionState()
+      state.toggleAt(15, false)
+      state.toggleAt(5, false)
+      state.toggleAt(10, false)
+      expect(state.getSelectedIndices()).toEqual([5, 10, 15])
+    })
+
+    it('returns ascending order even when setSelectedIndices is given non-sorted input', () => {
+      const state = createSelectionState()
+      state.setSelectedIndices([12, 3, 8, 1])
+      expect(state.getSelectedIndices()).toEqual([1, 3, 8, 12])
+    })
   })
 
   describe('clearSelection', () => {