feat(goal-mode): expose autonomous Goal Mode lifecycle (T-27)

[jaesbit]

Why

T-27: bring omp's Goal Mode to the cockpit so an objective can continue in a controlled way across turns, from the web session.

Scope

• Per-session Goal Mode bridge (apps/server/src/bridge/goal-mode-bridge.ts) over the SDK's real goalRuntime — create, pause, resume, cancel, and persistence hydration on resume (restored paused via goalRuntime.onThreadResumed()).
• WebSocket action transport and snapshot fields for goal state/progress (apps/server/src/bridge/{in-process,types}.ts, apps/server/src/ws.ts, packages/protocol/src/index.ts).
• /goal <objective> and /goal pause|resume|cancel composer commands (apps/web/src/components/Composer.tsx).
• Header status/progress display and pause/resume/cancel controls (apps/web/src/components/chat/ChatHeader.tsx).
• Store/reducer wiring and state hydration (apps/web/src/lib/{store,reducer,types}.ts).

Design notes

• goal-start/goal-continuation are hidden custom messages — autonomous turns never render as manual composer prompts.
• Plan Mode and Goal Mode are mutually exclusive: enabling Plan Mode pauses (not drops) a live goal; creating/resuming a goal exits Plan Mode first; cancel aborts a streaming goal before dropping it, then restores the previous tool set.

Testing

• Focused bridge tests (5), queue regression tests (8), reducer tests (17) — all pass.
• Server typecheck and web production build pass.
• No service restart performed as part of this work.