fix(antigravity): strip optional from tool schemas before Gemini

Closes #1537, #1841

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/translator/formats/gemini.js

@@ -19,7 +19,7 @@ export const UNSUPPORTED_SCHEMA_CONSTRAINTS = [
   // Dependency keywords (not supported)
   "dependencies", "dependentSchemas", "dependentRequired",
   // Other unsupported keywords
-  "title", "if", "then", "else", "contentMediaType", "contentEncoding",
+  "title", "optional", "if", "then", "else", "contentMediaType", "contentEncoding",
   // UI/Styling properties (from Cursor tools - NOT JSON Schema standard)
   "cornerRadius", "fillColor", "fontFamily", "fontSize", "fontWeight",
   "gap", "padding", "strokeColor", "strokeThickness", "textColor"