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/rate_limiter.py

@@ -24,6 +24,7 @@ from typing import Any
 
 logger = logging.getLogger(__name__)
 
+
 @dataclass
 class RateLimitConfig:
     """Configuration for rate limits at different time intervals."""
@@ -42,6 +43,7 @@ class RateLimitConfig:
             per_day=int(os.getenv(f"{env_prefix}RATE_LIMIT_PER_DAY", "10000")),
         )
 
+
 @dataclass
 class TokenBucket:
     """
@@ -110,6 +112,7 @@ class TokenBucket:
         tokens_needed = tokens - self.tokens
         return tokens_needed / self.refill_rate
 
+
 @dataclass
 class ClientRateLimitState:
     """Track rate limit state for a single client."""
@@ -188,6 +191,7 @@ class ClientRateLimitState:
             "uptime_seconds": uptime,
         }
 
+
 class RateLimiter:
     """
     Rate limiter using Token Bucket algorithm.
@@ -403,9 +407,11 @@ class RateLimiter:
             f"{config.per_minute}/min, {config.per_hour}/hour, {config.per_day}/day"
         )
 
+
 # Singleton instance
 _rate_limiter: RateLimiter | None = None
 
+
 def get_rate_limiter() -> RateLimiter:
     """Get or create the global rate limiter instance."""
     global _rate_limiter