test: repair route harness error rendering + stop AI-checker spawning real processes in tests (#97)

* fix(test): share route error handler with test harness + fix stale assertions

The route test harness built a bare Fastify instance without the production
global error handler (server.ts), so structured errors thrown by route helpers
(findSessionOrFail → 404, parseBody → 400) fell through to Fastify's default
handler — yielding a `{statusCode,error,message}` body instead of the
`{success:false,...}` shape, and the tests asserted the old implicit-200
behavior. 51 route tests across 7 files were red.

- Extract the handler into src/web/route-error-handler.ts; server.ts and the
  test harness now install the identical handler (single source of truth).
- Correct stale assertions across route test files: throw-based error paths
  now assert 404 (unknown session) / 400 (invalid body); genuine in-handler
  `return createErrorResponse(...)` paths (200 + success:false) left untouched.
- Reformat a few test files prettier flagged (pre-existing non-compliance).

Route suite: 307/307 passing (was 256/307). No production behavior change.

* test(respawn): mock child_process so AI checker never spawns real processes

respawn-controller.test.ts drives the AI idle checker (ai-checker-base), whose
runCheck() spawns a real `tmux new-session` running `claude -p`. The AI-enabled
tests only assert the ai_checking state transition (then cancel/stop), so the
spawn produced stray real tmux sessions and claude processes on every run — the
reason `npm test` (full suite) was unsafe to run inside a managed session.

Mock node:child_process here (mirroring ai-idle-checker.test.ts), spreading the
real module so `exec` stays intact for transitively-imported modules
(tmux-manager calls promisify(exec) at load). With this, the full non-mobile
suite runs without spawning any real tmux/claude.

---------

Co-authored-by: Teigen <teigen@TeigendeMac-mini.local>

src/web/route-error-handler.ts

@@ -0,0 +1,29 @@
+/**
+ * @fileoverview Shared Fastify error handler for Codeman's HTTP routes.
+ *
+ * Route helpers (`findSessionOrFail`, `parseBody` in route-helpers.ts) throw
+ * structured errors carrying `{ statusCode, body }`. This handler renders them
+ * into the proper HTTP response. It is installed by BOTH the production server
+ * and the route test harness so test behavior matches production exactly —
+ * without it, thrown errors fall through to Fastify's default handler and the
+ * response body is `{statusCode,error,message}` instead of `{success:false,...}`.
+ */
+import type { FastifyInstance } from 'fastify';
+import { ApiErrorCode, createErrorResponse, getErrorMessage } from '../types.js';
+
+/**
+ * Install the global error handler that renders structured route errors.
+ * Errors thrown with a `statusCode`/`body` (see route-helpers.ts) are sent
+ * verbatim at that status; anything else becomes a 500 OPERATION_FAILED response.
+ */
+export function installRouteErrorHandler(app: FastifyInstance): void {
+  app.setErrorHandler((error, _req, reply) => {
+    const statusCode = (error as { statusCode?: number }).statusCode ?? 500;
+    const body = (error as { body?: unknown }).body;
+    if (body) {
+      reply.code(statusCode).send(body);
+    } else {
+      reply.code(statusCode).send(createErrorResponse(ApiErrorCode.OPERATION_FAILED, getErrorMessage(error)));
+    }
+  });
+}

src/web/server.ts

@@ -89,8 +89,6 @@ const require = createRequire(import.meta.url);
 const { version: APP_VERSION } = require('../../package.json');
 import {
   getErrorMessage,
-  ApiErrorCode,
-  createErrorResponse,
   type PersistedRespawnConfig,
   type NiceConfig,
   type ImageDetectedEvent,
@@ -101,6 +99,7 @@ import { MAX_CONCURRENT_SESSIONS, MAX_SSE_CLIENTS } from '../config/map-limits.j
 import { SseEvent } from './sse-events.js';
 import type { ScheduledRun } from './ports/index.js';
 import { registerAuthMiddleware, registerSecurityHeaders } from './middleware/auth.js';
+import { installRouteErrorHandler } from './route-error-handler.js';
 import {
   registerPushRoutes,
   registerTeamRoutes,
@@ -657,16 +656,9 @@ export class WebServer extends EventEmitter {
       reply.code(updated ? 204 : 404).send();
     });
 
-    // Global error handler for structured errors thrown by findSessionOrFail
-    this.app.setErrorHandler((error, _req, reply) => {
-      const statusCode = (error as { statusCode?: number }).statusCode ?? 500;
-      const body = (error as { body?: unknown }).body;
-      if (body) {
-        reply.code(statusCode).send(body);
-      } else {
-        reply.code(statusCode).send(createErrorResponse(ApiErrorCode.OPERATION_FAILED, getErrorMessage(error)));
-      }
-    });
+    // Global error handler for structured errors thrown by findSessionOrFail /
+    // parseBody. Shared with the route test harness so test behavior matches prod.
+    installRouteErrorHandler(this.app);
 
     // Crash diagnostics beacon — frontend POSTs breadcrumbs, GET to read them
     let _crashBreadcrumbs = '';