feat: harden remote serve and reuse connections

- Gate TCP serve commands with safe-by-default policies, per-key allow tokens, per-key rate limiting, and audit labels.
- Reuse authenticated encrypted remote sessions and parallelize/caches multi-browser fanout to reduce repeated handshake roundtrips.
- Increase paged native-host batch size with extension-side byte budgeting to speed large tab listings safely.
- Point install output at public Chrome Web Store / Firefox AMO listings by default, with --dev preserving unpacked workflows.
- Share search-engine metadata between CLI and SDK and bump the package/extension version to 0.16.0.
- Cover the new security, pooling, paging, install, and fanout behavior with expanded Python and extension tests.

browser_cli/remote/socket.py

@@ -25,8 +25,8 @@ def split_endpoint(endpoint: str) -> tuple[str, int]:
   host, _, port_str = connect_ep.rpartition(":")
   return host, int(port_str)
 
-@contextmanager
-def open_socket(endpoint: str):
+def connect_socket(endpoint: str) -> socket.socket:
+  """Open and (on :443) TLS-wrap a socket. Caller owns closing it."""
   host, port = split_endpoint(endpoint)
   raw_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   raw_sock.settimeout(30)
@@ -40,6 +40,11 @@ def open_socket(endpoint: str):
   except Exception:
     raw_sock.close()
     raise
+  return sock
+
+@contextmanager
+def open_socket(endpoint: str):
+  sock = connect_socket(endpoint)
   with sock:
     yield sock