- Move MimeTypeToFileTypes and FileTypeToMimeType mappings to dedicated FileTypeMimeTypeMapping enum file
- Add empty content validation for file attachments
- Add PDF support for Gemini
- Display attachment references in user messages with file info
- Fix OpenAI unsupported mime type message formatting
- Improve URI list handling in InputService to include text/plain
- Update chat area padding and styling for better attachment display
- Prevent drag selection on chat padding element
- Update test assertions for new unsupported mime type message format
