feat: token-auth removal, security hardening, Stripe-style compat layer (v0.9.2)

- Remove token auth entirely; only Ed25519 pubkey auth or --no-auth
- Add 32 MB message-size cap in serve and client (DoS protection)
- Set Unix socket to 0o600 after bind in native_host (multi-user hardening)
- Enforce browser-cli/VERSION user-agent on all TCP connections
- Add PROTOCOL_MIN_CLIENT check (>= 0.9.0) server- and client-side
- Include server_version + min_client_version in challenge frame
- Add browser_cli/version_manager.py: parse_version, get_installed_version
- Add browser_cli/compat.py: Stripe-style versioning layer with adapt_request
  / adapt_response hooks; baseline 0.9.2, no shims needed yet
- Fix BrowserCLI key handling: no Path() wrap for agent specs
- Fix _multi_browser_targets() to forward key to remote_browser_targets()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

browser_cli/commands/windows.py

@@ -17,10 +17,10 @@ def _handle(command, args=None, profile=None):
         raise SystemExit(1)
 
 
-def _handle_multi(command, args=None, profile=None, remote=None, token=None):
+def _handle_multi(command, args=None, profile=None, remote=None):
     try:
         if remote:
-            return send_command(command, args or {}, profile=profile, remote=remote, token=token)
+            return send_command(command, args or {}, profile=profile, remote=remote)
         return send_command(command, args or {}, profile=profile)
     except (BrowserNotConnected, RuntimeError):
         return None
@@ -33,7 +33,7 @@ def _multi_browser_targets():
     remote = root.obj.get("remote")
     key = root.obj.get("key")
     if remote:
-        targets = remote_browser_targets(remote, root.obj.get("token"), key=key)
+        targets = remote_browser_targets(remote, key=key)
     else:
         targets = active_browser_targets(key=key)
     if len(targets) <= 1 and not any(target.remote for target in targets):
@@ -76,7 +76,7 @@ def windows_list():
     if targets:
         windows = []
         for target in targets:
-            result = _handle_multi("windows.list", profile=target.profile, remote=target.remote, token=target.token)
+            result = _handle_multi("windows.list", profile=target.profile, remote=target.remote)
             if result is None:
                 continue
             windows.extend({**window, "browser": target.display_name} for window in result)