- Use Mattermost file metadata/download API paths that work with current servers
- Buffer streamed content and post the final reply once for mobile clients that ignore post edits
- Keep attachment upload behavior on the first split chunk
- Send pairing code response (not empty message) for denied DMs
- Resolve actual channel type in action events before permission check
- Use word-boundary regex in _is_mentioned to avoid partial matches
- Use safe_filename for download path sanitization
- Add tests: denied DM pairing, denied action event, is_mentioned boundary
- Attachments now only attached to first chunk when message is split
- Filename sanitized with Path(name).name to prevent path traversal
- Updated streaming tests to match buffer-and-post-at-end pattern
(iOS compatibility)