docs: Update AGENTS.md with CI testing infrastructure details

- Documented the containerized CI approach using docker-compose.ci.yml
- Added instructions for local CI testing with test-ci-locally.sh
- Explained benefits of the approach (reproducibility, simplicity)
- Updated .gitignore to ignore SurrealDB data directory

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.gitignore

@@ -46,3 +46,6 @@ tests/playwright/.auth/
 
 # claude settings (keep .claude/CLAUDE.md but ignore user settings)
 .claude/settings.local.json
+
+# surrealdb data
+surreal/data/