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/core/session/tests/session.spec.ts

@@ -4,6 +4,7 @@ import { CallId } from '@deepseek-ai/dsh-llm'
 import SessionStore, {
   displayPromptContent,
   findLastMessageTurnEnd,
+  hasOpenTurn,
   SESSION_FORMAT_VERSION,
   Session,
   SessionEvent,
@@ -91,6 +92,17 @@ describe('Session', () => {
     expect(findLastMessageTurnEnd(session.events)).toBe(messageEnd)
   })
 
+  it('reports an open turn only between turn/start and its turn/end', () => {
+    const session = new Session(SessionId('open-turn'))
+    expect(hasOpenTurn(session.events)).toBe(false)
+    session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    expect(hasOpenTurn(session.events)).toBe(true)
+    session.append('user/message', { content: [{ type: 'text', text: 'x' }], source: { kind: 'user' } }, { surfaceOp: 'append' })
+    expect(hasOpenTurn(session.events)).toBe(true)
+    session.append('turn/end', { turn: 1, reason: { kind: 'completed' } })
+    expect(hasOpenTurn(session.events)).toBe(false)
+  })
+
   it('round-trips the coarse aborted turn outcome', () => {
     const session = new Session(SessionId('aborted'))
     session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })