test(editor): cover source-side self-move guard in the pre-remap ordering

Adds the case where the watcher's delete(old) arrives while the tab is
still at the old path (before remap re-homes it): with a live self-move
source stamp the tombstone must be suppressed. Pairs with the existing
naked-delete control (no stamp → deleted) to pin the guard's behavior.

Co-authored-by: Orca <help@stably.ai>

src/renderer/src/hooks/useEditorExternalWatch.test.ts

@@ -266,6 +266,22 @@ describe('createExternalWatchEventHandler tombstone coalescing', () => {
     dispose()
   })
 
+  it('does not tombstone a tab still at the old path when its delete is a self-move echo', () => {
+    // Pre-remap ordering: the watcher's delete(old) can arrive while the tab is
+    // still at the old path (remap hasn't run yet). Because the stamp is
+    // recorded before the rename, the source guard must still suppress the
+    // tombstone — the tab is about to be re-homed, not deleted.
+    recordSelfMove('/repo/notes.md', '/repo/subdir/notes.md')
+    const { handleFsChanged, dispose } = createExternalWatchEventHandler(findTarget)
+
+    handleFsChanged(payload([{ kind: 'delete', absolutePath: '/repo/notes.md' }]))
+    vi.advanceTimersByTime(200)
+
+    expect(setExternalMutation).not.toHaveBeenCalledWith('file-notes', 'deleted')
+    expect(setExternalMutation).not.toHaveBeenCalledWith('file-notes', 'renamed')
+    dispose()
+  })
+
   it('resolves batched delete+create in a single payload synchronously as renamed', () => {
     const { handleFsChanged, dispose } = createExternalWatchEventHandler(findTarget)
     handleFsChanged(