chore: remove unused prettier dep and dead code

Drop prettier (no config, script, or eslint integration), the unused render-semaphore state() method and CreateRenderSemaphore typedef, and ignore .claude/settings.local.json.

renderer/package.json

@@ -35,7 +35,6 @@
     "@types/react-dom": "19.2.3",
     "eslint": "10.6.0",
     "globals": "17.7.0",
-    "prettier": "3.9.4",
     "typescript": "6.0.3",
     "vitest": "4.1.10"
   }