refactor: configure Gemini reviewer to ignore lockfile and changelog

The bot doesn't provide much useful feedback on these files and pollutes release PRs, so we can just skip them.

(cherry picked from commit 870cc5d)

Author: dgp1130

.gemini/config.yaml

@@ -8,4 +8,6 @@ code_review:
     summary: false
     code_review: true
     include_drafts: false
-ignore_patterns: []
+ignore_patterns:
+  - pnpm-lock.yaml
+  - CHANGELOG.md