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/env.ts

@@ -32,6 +32,19 @@ export const env = {
       : 'network',
   jobImage:
     process.env.SPOON_AGENT_JOB_IMAGE?.trim() ?? 'spoon-agent-job:latest',
+  // Interactive terminal: image for the persistent shell container (defaults to
+  // the job image), the secret shared with the Next app for verifying terminal
+  // tokens, and how long an idle terminal container survives before cleanup.
+  terminalImage:
+    process.env.SPOON_AGENT_TERMINAL_IMAGE?.trim() ??
+    process.env.SPOON_AGENT_JOB_IMAGE?.trim() ??
+    'spoon-agent-job:latest',
+  terminalSecret:
+    process.env.SPOON_AGENT_TERMINAL_SECRET?.trim() ??
+    process.env.SPOON_AGENT_WORKER_INTERNAL_TOKEN?.trim() ??
+    process.env.SPOON_WORKER_TOKEN?.trim() ??
+    '',
+  terminalIdleMs: intEnv('SPOON_AGENT_TERMINAL_IDLE_MS', 1_800_000),
   workdir: process.env.SPOON_AGENT_WORKDIR?.trim() ?? '.local/agent-work',
   hostWorkdir: process.env.SPOON_AGENT_HOST_WORKDIR?.trim(),
   network: process.env.SPOON_AGENT_NETWORK?.trim(),