chore: ignore upstream paths in Renovate config

Ignore .github/, base-action/, and node_modules/ — these are
upstream-owned and managed via upstream-sync, not Renovate.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

renovate.json

@@ -1,6 +1,5 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "extends": [
+  "extends": ["local>renovate/renovate-config"],
-    "local>renovate/renovate-config"
+  "ignorePaths": [".github/**", "base-action/**", "node_modules/**"]
-  ]
 }