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/site_manager.py

@@ -24,6 +24,7 @@ from pydantic import BaseModel, ConfigDict, Field, ValidationInfo, field_validat
 
 logger = logging.getLogger(__name__)
 
+
 class SiteConfig(BaseModel):
     """
     Type-safe site configuration.
@@ -104,6 +105,7 @@ class SiteConfig(BaseModel):
         """
         return self.model_dump()
 
+
 class SiteManager:
     """
     Manage site configurations with type safety.
@@ -519,9 +521,11 @@ class SiteManager:
         counts_str = ", ".join(f"{k}: {v}" for k, v in counts.items())
         return f"SiteManager(total={self.get_count()}, {counts_str})"
 
+
 # Singleton instance
 _site_manager: SiteManager | None = None
 
+
 def get_site_manager() -> SiteManager:
     """
     Get the singleton site manager instance.