Worker: interactive terminal WebSocket bridge (PTY in workspace container)

- attachTerminalServer() upgrades /jobs/:id/terminal WS connections, verifying a
  short-lived job-scoped HMAC token (verifyTerminalToken) so the browser never
  holds the worker secret
- Bridges the socket to a bash PTY via dockerode exec (Tty) in a persistent
  per-job shell container (spoon-agent-term-<id>) mounting the workspace; binary
  frames = stdin, JSON text frames = resize; idle containers reaped after 30m
- New env: SPOON_AGENT_TERMINAL_IMAGE/SECRET/IDLE_MS (secret falls back to the
  shared worker internal token)

apps/agent-worker/src/server.ts

@@ -4,6 +4,7 @@ import type { IncomingMessage, ServerResponse } from 'node:http';
 import type { Id } from '@spoon/backend/convex/_generated/dataModel.js';
 
 import { env } from './env';
+import { attachTerminalServer } from './terminal';
 import {
   abortWorkspaceAgent,
   cleanupOrphanedWorkspaces,
@@ -182,6 +183,7 @@ export const startWorkerServer = () => {
 	      }
     })();
   });
+  attachTerminalServer(server);
   server.listen(env.httpPort, () => {
     console.log(
       `Spoon agent worker HTTP server listening on port ${env.httpPort}`,