feat(v0.3): H2 server — Claude Code hooks → live status side-channel

- types: ClaudeStatus + ServerMessage 'status'; Session.claudeStatus;
  SessionManager.handleHookEvent
- session: inject WEBTERM_SESSION + WEBTERM_HOOK_URL into the spawned shell env
  so hooks know which tab they belong to
- http/hook.ts: pure event→status mapper (PreToolUse→working, PermissionRequest/
  Notification:permission_prompt→waiting, Stop/idle_prompt→idle); 6 unit tests
- server: POST /hook (loopback-only, express.json 64kb) → manager pushes 'status'
- fix: closeIdleConnections() on shutdown so an idle hook keep-alive socket
  doesn't hang close()/SIGTERM
- integration ⑦ (real PTY): attach → POST /hook → ws receives status. 205 tests green.

src/http/hook.ts

@@ -0,0 +1,57 @@
+/**
+ * src/http/hook.ts (H2) — map a Claude Code hook POST to a session status update.
+ *
+ * Pure + never throws. The web-terminal sessionId arrives in the
+ * `X-Webterm-Session` header (injected as $WEBTERM_SESSION on spawn); the hook
+ * payload arrives as JSON in the body. We translate the event into a coarse
+ * ClaudeStatus the UI can show. The server is still a byte-shuttle for the
+ * terminal stream — this is an out-of-band side-channel.
+ */
+
+import type { ClaudeStatus } from '../types.js';
+
+export interface HookEvent {
+  sessionId: string;
+  status: ClaudeStatus;
+  detail?: string;
+}
+
+/**
+ * @param sessionId value of the `X-Webterm-Session` header
+ * @param body parsed JSON body of the hook POST (untrusted)
+ * @returns a status update, or null if the payload is unusable
+ */
+export function parseHookEvent(sessionId: string | undefined, body: unknown): HookEvent | null {
+  if (typeof sessionId !== 'string' || sessionId.length === 0) return null;
+  if (body === null || typeof body !== 'object') return null;
+
+  const b = body as Record<string, unknown>;
+  const event = typeof b['hook_event_name'] === 'string' ? b['hook_event_name'] : '';
+  const notif = typeof b['notification_type'] === 'string' ? b['notification_type'] : '';
+  const tool = typeof b['tool_name'] === 'string' ? b['tool_name'] : undefined;
+
+  let status: ClaudeStatus;
+  switch (event) {
+    case 'PreToolUse':
+    case 'PostToolUse':
+    case 'UserPromptSubmit':
+      status = 'working';
+      break;
+    case 'PermissionRequest':
+      status = 'waiting';
+      break;
+    case 'Stop':
+    case 'SessionEnd':
+      status = 'idle';
+      break;
+    case 'Notification':
+      status = notif === 'permission_prompt' ? 'waiting' : 'idle';
+      break;
+    default:
+      return null;
+  }
+
+  return status === 'waiting' && tool !== undefined
+    ? { sessionId, status, detail: tool }
+    : { sessionId, status };
+}