fix(editor): flavor-aware trailing-separator strip; preserve POSIX literal backslashes

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

src/renderer/src/lib/remap-open-editor-tabs-for-path-change.test.ts

@@ -307,6 +307,30 @@ describe('remapOpenEditorTabsForPathChange', () => {
     expect(useAppStore.getState().openFiles[0]!.filePath).toBe('/repo/dst/a\\b.txt')
   })
 
+  it('does not strip a trailing backslash from a POSIX destination directory name', () => {
+    const state = useAppStore.getState()
+    state.openFile(
+      {
+        filePath: '/repo/src/a.ts',
+        relativePath: 'src/a.ts',
+        worktreeId: 'wt-1',
+        language: 'typescript',
+        mode: 'edit'
+      },
+      { suppressActiveRuntimeFallback: true }
+    )
+
+    // Destination directory is literally named `dst\` (legal on POSIX).
+    remapOpenEditorTabsForPathChange({
+      fromPath: '/repo/src',
+      toPath: '/repo/dst\\',
+      worktreePath: '/repo',
+      worktreeId: 'wt-1'
+    })
+
+    expect(useAppStore.getState().openFiles[0]!.filePath).toBe('/repo/dst\\/a.ts')
+  })
+
   it('keeps `/` for a POSIX destination whose ancestor contains a legal backslash', () => {
     const state = useAppStore.getState()
     state.openFile(

src/renderer/src/lib/remap-open-editor-tabs-for-path-change.ts

@@ -30,7 +30,11 @@ function stripTrailingSeparators(path: string): string {
   if (path === '/' || /^[A-Za-z]:[\\/]?$/.test(path)) {
     return normalizeRuntimePathSeparators(path)
   }
-  return normalizeRuntimePathSeparators(path).replace(/\/+$/, '')
+  // Only fold backslashes to `/` for Windows/UNC paths; on POSIX a backslash is
+  // legal filename data and must not be treated as a separator.
+  return isWindowsAbsolutePathLike(path)
+    ? normalizeRuntimePathSeparators(path).replace(/\/+$/, '')
+    : path.replace(/\/+$/, '')
 }
 
 function deriveRelativeRootFromOpenFile(filePath: string, relativePath: string): string {
@@ -94,14 +98,14 @@ function computeMovedPath(fromPath: string, toPath: string, filePath: string): s
   if (suffix === '') {
     return toPath
   }
-  const strippedToPath = toPath.replace(/[\\/]+$/, '')
   // Flavor by SYNTAX (drive/UNC), never by "contains a backslash": a POSIX/SSH
-  // path may hold a legal backslash, so it must keep `/` and never gain one.
+  // path may hold a legal backslash, so it must keep `/`, never gain one, and
+  // never have a trailing backslash stripped as if it were a separator.
   if (isWindowsAbsolutePathLike(toPath)) {
     const separator = toPath.includes('\\') ? '\\' : '/'
-    return `${strippedToPath}${separator}${suffix.split('/').join(separator)}`
+    return `${toPath.replace(/[\\/]+$/, '')}${separator}${suffix.split('/').join(separator)}`
   }
-  return `${strippedToPath}/${suffix}`
+  return `${toPath.replace(/\/+$/, '')}/${suffix}`
 }
 
 function getRelativePathFromRoot(rootPath: string, candidatePath: string): string {