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/serve/proxy.py

@@ -18,6 +18,7 @@ class ServeProxyMixin:
   command: str
   compress: bool
   accept_encoding: dict | None
+  auth_label: str | None
 
   async def send_error(self, msg: str, msg_id=None) -> None: ...
   async def send_payload(self, data: bytes) -> None: ...
@@ -35,7 +36,7 @@ class ServeProxyMixin:
       sock_path = resolve_socket(resolved_profile)
     except BrowserNotConnected as e:
       await self.send_error(str(e))
-      log_request(self.addr, self.command, resolved_profile, "ERROR", "browser not connected")
+      log_request(self.addr, self.command, resolved_profile, "ERROR", "browser not connected", identity=self.auth_label)
       return
 
     try:
@@ -46,7 +47,7 @@ class ServeProxyMixin:
       await self.send_browser_response(adapt_response(resp_payload, self.command, self.client_ver), resolved_profile)
     except (OSError, json.JSONDecodeError, ConnectionError) as e:
       await self.send_error(str(e))
-      log_request(self.addr, self.command, resolved_profile, "ERROR", str(e))
+      log_request(self.addr, self.command, resolved_profile, "ERROR", str(e), identity=self.auth_label)
 
   async def _windows_roundtrip(self, sock_path: str, payload: bytes) -> bytes:
     from multiprocessing.connection import Client as PipeClient
@@ -74,6 +75,6 @@ class ServeProxyMixin:
     else:
       await self.send_payload(resp_payload)
     if resp_data.get("success", True):
-      log_request(self.addr, self.command, resolved_profile, "OK")
+      log_request(self.addr, self.command, resolved_profile, "OK", identity=self.auth_label)
     else:
-      log_request(self.addr, self.command, resolved_profile, "ERROR", resp_data.get("error", ""))
+      log_request(self.addr, self.command, resolved_profile, "ERROR", resp_data.get("error", ""), identity=self.auth_label)