- GET /api/file returns ETag (mtime+size) + X-Writable on disk files;
PUT /api/file accepts optional if_match -> 409 Conflict on stale version
(last-write-wins preserved when omitted), echoes the new ETag
- FileViewerBase: View | Edit tabs for .md when the caller can write;
source textarea with Save/Cancel, live preview while editing
- Watcher no longer clobbers the buffer mid-edit: while editing with
unsaved changes it probes the server ETag and only raises a conflict
when the remote actually moved on (own-save echo is ignored)
- Conflict banner: Reload remote | Copy mine, then reload | Overwrite
- i18n (en/it/fr) + CSS; docs/projects.md updated