- Add ?embed=1 to /pages/{id} route, passes embed_mode to template
- base.html: embed-mode class hides sidebar/topbar, removes margins
- Replace peek-body content with iframe loading /pages/{id}?embed=1
in both library.html and local_workspace.html
- Remove async content loading (now editor handles rendering)
- Add resize handle on left edge of peek panels (both library + local-ws)
- Click without drag: closes panel
- Click + drag horizontal: resizes panel width (300px to 90vw)
- Width persisted in localStorage (fd_peek_width)
- 100% code reuse: editor runs same /pages/{id} with embed flag