Restructure chat service, web routes, and add test suite

Split monolithic chat service into modular structure with Matrix client
support, extract web server into per-resource route modules, introduce
bootstrap/main-loop separation, and add comprehensive vitest coverage
across services, repositories, and utilities. Adds project docs and
CLAUDE.md agent instructions.

src/utils/fetch-with-timeout.ts

@@ -0,0 +1,18 @@
+/**
+ * `fetch` with a hard client-side timeout. Node's global fetch otherwise
+ * inherits no timeout — a stalled connection will hang the caller forever,
+ * which has wedged the main loop more than once (incidents on 2026-05-20).
+ *
+ * On timeout, throws an error whose `.name === 'TimeoutError'`. Callers that
+ * want to differentiate timeout-vs-other failures can branch on that.
+ */
+export async function fetchWithTimeout(
+  input: string | URL | Request,
+  init: RequestInit & { timeoutMs?: number } = {},
+): Promise<Response> {
+  const { timeoutMs = 30_000, ...rest } = init;
+  return fetch(input, {
+    ...rest,
+    signal: AbortSignal.timeout(timeoutMs),
+  });
+}