chore: update gitignore

- Ignore docs/plans/*.md
- Ignore .agents directory

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

Author: jiangtao

.gitignore

@@ -16,4 +16,6 @@ shares/*.pptx
 home/node_modules/
 home/public/
 home/.deploy_git/
-home/db.json
+home/db.json
+docs/plans/*.md
+.agents