The "What reviewers will see" window now has a sidebar like the explorer's
instead of the one-row file strip: folders first, then files, with the
explorer's tree rows, icons and teal selection on the README. Folders expand
from the loaded file list. The sidebar is 24% of the window (180-240px),
tinted full height, and scrolls apart from the document. Phones hide it and
show the explorer's "Files" button in the file bar. Loading shows skeleton
rows; without a file list the sidebar shows the README only.
Removes the strip fitter and the dead rail/strip CSS.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>