fix(ci): fix black/ruff failures, add CoC and PR template

- Fix Python formatting (sync no longer strips blank lines from .py files)
- Remove test_community_build.py (tests private sync module)
- Fix ruff warnings in test files
- Add CODE_OF_CONDUCT.md
- Add .github/PULL_REQUEST_TEMPLATE.md

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

core/oauth/server.py

@@ -16,6 +16,7 @@ from .token_manager import get_token_manager
 
 logger = logging.getLogger(__name__)
 
+
 class OAuthError(Exception):
     """OAuth error with error code and description"""
 
@@ -25,6 +26,7 @@ class OAuthError(Exception):
         self.status_code = status_code
         super().__init__(error_description)
 
+
 class OAuthServer:
     """
     OAuth 2.1 Authorization Server
@@ -385,9 +387,11 @@ class OAuthServer:
             scope=" ".join(requested_scopes),
         )
 
+
 # Singleton
 _oauth_server: OAuthServer | None = None
 
+
 def get_oauth_server() -> OAuthServer:
     """Get singleton OAuthServer instance"""
     global _oauth_server