fix(antigravity): add propertyNames to incompatible schema keywords (#52)

Adds 'propertyNames' to the list of JSON Schema validation keywords that are stripped from tool schemas when converting for Claude via the Antigravity provider. This keyword is not supported by Google's Proto-based API and was causing 400 Bad Request errors with nested object schemas.

Closes #48

Co-authored-by: mirrobot-agent[bot] <2140342+mirrobot-agent@users.noreply.github.com>

Author: mirrobot-agent[bot]

src/rotator_library/providers/antigravity_provider.py

@@ -549,6 +549,7 @@ def _clean_claude_schema(schema: Any, for_gemini: bool = False) -> Any:
         "format",
         "minProperties",
         "maxProperties",
+        "propertyNames",
         "contentEncoding",
         "contentMediaType",
         "contentSchema",