Per-file viewer LiveComponent: <Fresco.canvas> + <Etcher.layer> for images, video / PDF / icon fallback for other types, plus a sidebar with filename + Download + metadata + comments thread. Owns the annotation lifecycle (composer popover, persistence sync via EtcherAdapter, the patch-shape / delete-shape JS bridges).

Shared between MediaBrowser (admin file grid → click image → modal) and MediaViewer (lightbox embedded by MediaGallery and other consumers). Both parents own their own modal shell + prev/next navigation; this component is just the per-file content.

Required assigns

• :id — DOM id, must include the file uuid so the parent's prev/next navigation remounts the component on file change (and Fresco's phx-update="ignore" canvas DOM is replaced wholesale with the new file's image).
• :file — curated file map (%{file_uuid, mime_type, urls, filename, file_type, size, inserted_at, ...}). Same shape MediaBrowser's uploaded_files carries.
• :current_user — logged-in user; nil-tolerant. When nil the composer + comments thread don't render (no user to attribute a comment to).
• :parent_id — DOM id of the outer LiveComponent (the modal host). Currently unused by this component, but kept on the assigns map so future cross-component send_updates have a target without re-plumbing the API.