- Consolidate extractImageKey/extractFileKey/extractFileName into shared
extractJSONStringField helper to reduce code duplication
- Move mentionPlaceholderRegex to package-level position after imports
- Rename feishuCfg field to config for clarity within FeishuChannel
- Replace @_user_1 heuristic with GET /open-apis/bot/v3/info API call
at startup for reliable bot @mention detection
- Fix double close on file handle in downloadResource by removing defer
and using explicit close in both success and error paths
- Add unit tests for common.go and feishu_64.go helpers (53 test cases)
Hoshina