feat(web): permission presets and approval answering for the web UI

The web host now composes the sandboxed product path (sandbox-local +
sandbox-policy behind bash-sandbox/fs-sandbox, with user-approval and
permission on top); BootHostOptions.sandbox carries the deployment
defaults (workspace-write + ask).

createApiProxy owns the approval pending registry: a ctx.approval ask
becomes an answerable approval/requested mux frame with a stable rpcId,
replayed verbatim on every mux open until settled; respond routes by the
echoed rpcId, validates the ApprovalResponsePayload audit correlation,
and broadcasts approval/resolved; the ask's abort signal withdraws the
question as cancelled.

session.permissions / session.setPermission project ctx.permission into
a protocol-owned PermissionOption select; idle switches are held
last-write-wins and
flushed into the next prompted turn (the ACP bridge's anchoring
pattern). The shared hasOpenTurn fold moved to dsh-session,
deduplicating the private copies in user-approval, the ACP bridge, and
the proxy.

Client, per the designer draft: a pending approval takes over the
composer (ApprovalPanel replaces the InputBar — amber strip,
justification headline, paired command, one-shot refuse/allow, keyed by
rpcId so a queued second approval remounts live; the resolved frame
restores the composer); the sidebar session row shows an amber
waiting-approval dot that outranks the running ring (manager-tracked
approvalId set, idempotent under mux-open replays, cleared per
connection generation, lit for uninstantiated sessions too); the
permission selector is a composer bottom-row chip over an invisible
native select, with a presentation-only title-case transform
(workspace-write renders as Workspace Write; wire names untouched). Question placeholders stay in the message flow. The
connection fixture mirrors the host behavior for keyless browser
acceptance.

packages/client/ui-conversation/tests/chat-branch-tails.spec.tsx

@@ -44,11 +44,11 @@ describe('MessageItem arms', () => {
 })
 
 describe('small branch tails', () => {
-  it('PendingCard approval reason renders when present', () => {
+  it('PendingCard renders the question count', () => {
     const view = render(
-      <PendingCard item={new PendingWait('approval', RpcId('r1'), 's1' as SessionId, { approvalId: 'a1', toolName: 'rm', reason: 'careful' } as PendingWait<'approval'>['payload'], vi.fn())} />,
+      <PendingCard item={new PendingWait('question', RpcId('r1'), 's1' as SessionId, { questions: [{ id: 'q1', question: '选择' }] } as PendingWait<'question'>['payload'], vi.fn())} />,
     )
-    expect(view.getByText('careful')).toBeTruthy()
+    expect(view.getByText(/等待回答（1 题）/)).toBeTruthy()
   })
 
   it('AssistantMarkdown single-line reasoning summary skips the newline cut', () => {