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/token_manager.py

@@ -17,11 +17,13 @@ from .storage import get_storage
 
 logger = logging.getLogger(__name__)
 
+
 class SecurityError(Exception):
     """Security-related error (e.g., token reuse)"""
 
     pass
 
+
 class TokenManager:
     """
     OAuth 2.1 Token Manager.
@@ -302,9 +304,11 @@ class TokenManager:
         # Access tokens cannot be revoked (JWT stateless)
         # They expire naturally after TTL
 
+
 # Singleton
 _token_manager: TokenManager | None = None
 
+
 def get_token_manager() -> TokenManager:
     """Get singleton TokenManager instance"""
     global _token_manager