feat: add remote trust and server identity pinning

- Add SSH-style server identity keys and known-host verification for remote serve endpoints.
- Add remote add/list/remove commands for explicit endpoint persistence.
- Fix remote clients listing to fan out through target discovery instead of ambiguous auto-routing.
- Add URL glob matching for tabs filter and count with extension tests.
- Add n8n credential pinning for server public keys or SHA256 fingerprints.
- Remove obsolete compat shim behavior while keeping empty compat seams for future protocol changes.
- Bump browser-cli to 0.16.4 and n8n node to 0.3.1.
- Cover known-hosts, remote registry, compat seams, n8n protocol verification, and URL matching with tests.

browser_cli/remote/transport.py

@@ -28,6 +28,7 @@ from browser_cli.remote.socket import (
   split_endpoint as _split_endpoint,
 )
 from browser_cli.remote import pool as _pool
+from browser_cli.remote.known_hosts import verify_known_host
 
 def _send_remote(endpoint: str, msg: dict, private_key=None, *, warn_no_pq: bool | None = None) -> bytes | None:
   # Reuse an already-authenticated connection when one is idle for this endpoint.
@@ -51,7 +52,10 @@ def _send_remote_handshake(endpoint: str, msg: dict, private_key=None, *, warn_n
 
   sock = _connect_socket(endpoint)
   try:
-    payload_msg, pq_shared_secret = _with_challenge(_recv_all(sock), msg, private_key, build_auth)
+    challenge_raw = _recv_all(sock)
+    challenge, _nonce_hex = _parse_challenge(challenge_raw)
+    verify_known_host(endpoint, challenge)
+    payload_msg, pq_shared_secret = _with_challenge(challenge_raw, msg, private_key, build_auth)
     sock.sendall(frame(json.dumps(payload_msg).encode("utf-8")))
     response = _decode_pq_response(_recv_all(sock), pq_shared_secret)
   except BaseException:
@@ -69,6 +73,8 @@ async def _send_remote_async(endpoint: str, msg: dict, private_key=None, *, warn
   reader, writer = await _open_async_connection(endpoint)
   try:
     challenge_raw = await _async_recv_all(reader)
+    challenge, _nonce_hex = _parse_challenge(challenge_raw)
+    verify_known_host(endpoint, challenge)
     warn = _should_warn_no_pq(msg) if warn_no_pq is None else warn_no_pq
 
     async def build_auth(sync_msg: dict, challenge: dict | None, nonce_hex: str | None, key):