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/csrf.py

@@ -10,6 +10,7 @@ Part of Phase E: Custom OAuth Authorization Page
 import secrets
 import time
 
+
 class CSRFTokenManager:
     """
     Manages CSRF tokens for OAuth authorization requests.
@@ -107,9 +108,11 @@ class CSRFTokenManager:
             "token_lifetime_seconds": self._token_lifetime,
         }
 
+
 # Global CSRF token manager instance
 _csrf_manager: CSRFTokenManager | None = None
 
+
 def get_csrf_manager() -> CSRFTokenManager:
     """
     Get the global CSRF token manager instance.