In Compare each pane renders into a sandboxed <iframe>. A file dropped on
a pane was handled by the iframe (browser default), so the browser loaded
the file *inside* the pane — appearing 'behind' the app — instead of
attaching it. The existing #chat-container drop handler never sees the
event because drag events don't bubble out of an iframe.
While a file drag is active in Compare, raise a single full-window drop
shield above the panes/iframes so the drop lands on the parent document,
then route the files into the shared composer (the same pending-files
pipeline the file picker and paste already use). Scoped to Compare via the
.compare-active class, so normal chat and the tool dropzones (gallery, RAG,
document editor, …) are unaffected.
Verified with a headless-Chromium integration test: synthetic file
dragover raises the shield, drop attaches the file to the composer, and
non-Compare mode is unaffected. Also ran node --check static/app.js.
Follow-up to #271. Skip svgifyEmoji when body.text-emojis is set so
deEmojify can strip Unicode from replies; also unwrap existing .emoji
spans from messages rendered before the setting was applied.
Related to #270
