Document who can call the loopback API and let the user pick the listen port.

AGENTS.md

@@ -12,7 +12,7 @@ Do not edit `places.sqlite` while Firefox is open if this API is reachable.
 2. Native host installed only if scripts should call in: `powershell -NoProfile -File tools/install-native-host.ps1`
 3. Firefox **running** for those calls
 
-If `http://127.0.0.1:17634/health` fails, the host is not up. If `/health` works but calls 401, you do not have a current token.
+If `http://127.0.0.1:17634/health` fails, the host is not up or the listen port was changed in Manage clients. If `/health` works but calls 401, you do not have a current token. Use `FAB_URL` when the port is not the default.
 
 ## Auth
 
@@ -89,7 +89,7 @@ REST aliases use the same Bearer token. `GET /health` has no token (loopback liv
 
 | Symptom | Cause | What to do |
 |---------|--------|------------|
-| Connection refused on `:17634` | Firefox closed or add-on/host missing | Open Firefox; load add-on; install native host |
+| Connection refused on the listen port | Firefox closed, add-on/host missing, or port changed | Open Firefox; load add-on; install native host; match `FAB_URL` to Manage clients |
 | 401 `Bearer token required` | Unsigned request | Set `FAB_TOKEN` |
 | 401 `unknown token` | Revoked, typo, or never generated | Manage clients → generate again |
 | 502 `method not allowed` | Typo or API not in the allowlist | `meta.methods` |