phsl / new-api

- Store editing message object reference using useRef to avoid ID conflicts
- Use object reference comparison first before falling back to ID matching
- Apply fix to both save and cancel operations in message editing
- Clear reference after edit completion to prevent stale object issues

Previously, when editing imported messages that contained duplicate IDs,
the findIndex operation would match the first occurrence rather than the
intended message, causing conversation history truncation when saving
edits. This change stores and uses object references for accurate message
identification during the editing process.