fix(host): review round 5 — draft-pending action gating, in-flow errors, IME guards

- Open and New folder disable while a path draft is uncommitted: targetPath
  still names the previous selection/listing, and committing against it
  while a different path shows in the header adopts the wrong directory.
- The Miller columns keep their own row so a status/error line renders below
  them inside the card instead of competing as a third flex item the dialog
  clips off-screen.
- Both text inputs (path editor, folder name) carry the IME composition
  guard the workspace-name inputs already had: a composing Enter confirms
  the candidate, never submits.

packages/host/directory-picker-browse/src/client/DirectoryBrowser.module.css

@@ -41,6 +41,16 @@
 
 /* Deep chains scroll inside the trail (the effect pins the tail into view)
  * so the edit zone to the right never leaves the bar. */
+/* The Miller columns keep their own row so a status/error line below never
+ * competes with the fixed column widths for horizontal space. */
+.millerRow {
+  display: flex;
+  align-items: stretch;
+  flex: 1 1 0;
+  min-height: 0;
+  gap: 20px;
+}
+
 .crumbTrail {
   display: flex;
   align-items: center;
@@ -113,10 +123,9 @@
  * the hairline divider centered between them; each column scrolls alone. */
 .content {
   display: flex;
-  align-items: stretch;
+  flex-direction: column;
   flex: 1 1 0;
   min-height: 0;
-  gap: 20px;
   padding: 16px 24px 0;
 }
 

packages/host/directory-picker-browse/src/client/DirectoryBrowser.tsx

@@ -120,6 +120,9 @@ export function DirectoryBrowser({ open, listDirectory, createDirectory, onOpen,
   // Deep ancestry overflows the trail; keep its tail (the current directory
   // and the edit zone beside it) in view whenever the chain changes.
   const crumbTrailRef = useRef<HTMLSpanElement | null>(null)
+  // IME confirmation (Enter selecting a candidate) must not submit either
+  // text input; the same guard the workspace-name inputs carry.
+  const composingRef = useRef(false)
 
   /** Replace the whole view with one freshly listed level (no selection). */
   const navigate = useCallback((path?: string) => {
@@ -242,6 +245,10 @@ export function DirectoryBrowser({ open, listDirectory, createDirectory, onOpen,
   // focus trap, so every parent control goes inert (Shift-Tab or AT must not
   // close, adopt, or retarget underneath the child).
   const parentInert = busy || folderDraft !== null
+  // An uncommitted path draft makes targetPath stale relative to the header:
+  // committing actions must not act on the previous selection/listing while
+  // a different path is displayed.
+  const draftPending = pathDraft !== null
 
   return (
     <Modal
@@ -298,8 +305,10 @@ export function DirectoryBrowser({ open, listDirectory, createDirectory, onOpen,
                 autoFocus
                 disabled={parentInert}
                 onChange={(event) => { setPathDraft(event.target.value) }}
+                onCompositionStart={() => { composingRef.current = true }}
+                onCompositionEnd={() => { composingRef.current = false }}
                 onKeyDown={(event) => {
-                  if (event.key === 'Enter') {
+                  if (event.key === 'Enter' && !composingRef.current) {
                     event.preventDefault()
                     const target = pathDraft.trim()
                     if (target !== '') navigate(target)
@@ -315,25 +324,27 @@ export function DirectoryBrowser({ open, listDirectory, createDirectory, onOpen,
         </div>
       </div>
       <div className={css.content}>
-        {parent !== null && (
-          <LevelColumn
-            entries={parent.entries}
-            selectedPath={selected?.path ?? null}
-            busy={parentInert}
-            onPick={select}
-            wide={!twoPane}
-          />
-        )}
-        {twoPane && <span className={css.divider} />}
-        {twoPane && child !== null && (
-          <LevelColumn
-            entries={child.entries}
-            selectedPath={null}
-            busy={parentInert}
-            onPick={advance}
-            wide={false}
-          />
-        )}
+        <div className={css.millerRow}>
+          {parent !== null && (
+            <LevelColumn
+              entries={parent.entries}
+              selectedPath={selected?.path ?? null}
+              busy={parentInert}
+              onPick={select}
+              wide={!twoPane}
+            />
+          )}
+          {twoPane && <span className={css.divider} />}
+          {twoPane && child !== null && (
+            <LevelColumn
+              entries={child.entries}
+              selectedPath={null}
+              busy={parentInert}
+              onPick={advance}
+              wide={false}
+            />
+          )}
+        </div>
         {loading && <div className={css.status} role="status">{t('browser.loading')}</div>}
         {error !== null && <div className={css.error} role="alert">{error}</div>}
       </div>
@@ -341,7 +352,7 @@ export function DirectoryBrowser({ open, listDirectory, createDirectory, onOpen,
         <Button
           variant="outline"
           icon={<IconPlusOutline16 size={14} />}
-          disabled={parent === null || loading || parentInert}
+          disabled={parent === null || loading || parentInert || draftPending}
           onClick={() => {
             setFolderDraft('')
             setCreateError(null)
@@ -354,7 +365,7 @@ export function DirectoryBrowser({ open, listDirectory, createDirectory, onOpen,
         <Button
           variant="primary"
           className={clsx(css.footerAction)}
-          disabled={targetPath === null || loading || parentInert}
+          disabled={targetPath === null || loading || parentInert || draftPending}
           /* v8 ignore next -- narrowing guard: Open disables while no target exists. */
           onClick={() => { if (targetPath !== null) onOpen(targetPath) }}
         >
@@ -380,8 +391,10 @@ export function DirectoryBrowser({ open, listDirectory, createDirectory, onOpen,
             autoFocus
             disabled={creatingFolder}
             onChange={(event) => { setFolderDraft(event.target.value) }}
+            onCompositionStart={() => { composingRef.current = true }}
+            onCompositionEnd={() => { composingRef.current = false }}
             onKeyDown={(event) => {
-              if (event.key === 'Enter') {
+              if (event.key === 'Enter' && !composingRef.current) {
                 event.preventDefault()
                 confirmCreate()
               }

packages/host/directory-picker-browse/tests/directory-browser.spec.tsx

@@ -284,6 +284,59 @@ describe('DirectoryBrowser', () => {
     await waitFor(() => { expect(screen.getByText('harness')).toBeTruthy() })
   })
 
+  it('disables Open and New folder while a path draft is uncommitted', async () => {
+    mount()
+    await waitFor(() => { expect(screen.getByRole('listitem')).toBeTruthy() })
+    fireEvent.click(screen.getByRole('button', { name: 'browser.editPath' }))
+    // targetPath still names the previous listing; committing actions must
+    // not act on it while a different path is displayed in the header.
+    expect(screen.getByRole<HTMLButtonElement>('button', { name: 'browser.open' }).disabled).toBe(true)
+    expect(screen.getByRole<HTMLButtonElement>('button', { name: 'browser.newFolder' }).disabled).toBe(true)
+    fireEvent.keyDown(screen.getByLabelText('browser.editPath'), { key: 'Escape' })
+    expect(screen.getByRole<HTMLButtonElement>('button', { name: 'browser.open' }).disabled).toBe(false)
+  })
+
+  it('ignores Enter while an IME composition is active in either input', async () => {
+    const b = mount()
+    await waitFor(() => { expect(screen.getByRole('listitem')).toBeTruthy() })
+    // Path editor: a composing Enter confirms the candidate, not the path.
+    fireEvent.click(screen.getByRole('button', { name: 'browser.editPath' }))
+    const pathInput = screen.getByLabelText('browser.editPath')
+    fireEvent.change(pathInput, { target: { value: DOCS } })
+    const listCalls = b.listDirectory.mock.calls.length
+    fireEvent.compositionStart(pathInput)
+    fireEvent.keyDown(pathInput, { key: 'Enter' })
+    expect(b.listDirectory.mock.calls.length).toBe(listCalls)
+    fireEvent.compositionEnd(pathInput)
+    fireEvent.keyDown(pathInput, { key: 'Enter' })
+    await waitFor(() => { expect(b.listDirectory).toHaveBeenLastCalledWith(DOCS) })
+    // Create dialog: same guard.
+    fireEvent.click(screen.getByRole('button', { name: 'browser.newFolder' }))
+    const nameInput = screen.getByLabelText('browser.folderName')
+    fireEvent.change(nameInput, { target: { value: '新建' } })
+    fireEvent.compositionStart(nameInput)
+    fireEvent.keyDown(nameInput, { key: 'Enter' })
+    expect(b.createDirectory).not.toHaveBeenCalled()
+    fireEvent.compositionEnd(nameInput)
+    fireEvent.keyDown(nameInput, { key: 'Enter' })
+    await waitFor(() => { expect(b.createDirectory).toHaveBeenCalledWith(DOCS, '新建') })
+  })
+
+  it('surfaces a two-pane navigation failure as an alert below the columns', async () => {
+    const b = mount()
+    await waitFor(() => { expect(screen.getByRole('listitem')).toBeTruthy() })
+    fireEvent.click(rowButton(screen.getByRole('listitem')))
+    await waitFor(() => { expect(columns()).toHaveLength(2) })
+    b.listDirectory.mockImplementation(async () => {
+      throw new DirectoryBrowseError({ code: 'directory-unreadable', message: 'denied', details: { path: HOME } })
+    })
+    fireEvent.click(within(screen.getByRole('navigation')).getByRole('button', { name: 'browser.home' }))
+    await waitFor(() => { expect(screen.getByRole('alert').textContent).toBe('denied') })
+    // Both panes survive the failure; the alert renders in the flow, not as a
+    // third column competing for the fixed widths.
+    expect(columns()).toHaveLength(2)
+  })
+
   it('ignores dismissal while adoption is busy', async () => {
     const b = mount({ busy: true })
     await waitFor(() => { expect(screen.getByRole('dialog')).toBeTruthy() })