Add line-by-line diff view for artifact updates (#2310)
* Show a scrollable diff when opening an edited artifact
Clicking an "Edited" artifact card now opens the panel on the Code tab
showing the full file as a line diff against the previous version:
changed lines get git-style +/- prefixes and tinted full-width bands
(reusing the hljs addition/deletion theme classes), and the view
auto-scrolls to the first change. A floating toggle next to the word
wrap button switches between the diff and the plain code, and the
footer shows +added/-removed line counts.
The diff utility trims common prefix/suffix lines before running an
LCS alignment, so even large artifacts with small edits stay cheap,
and falls back to delete-all/add-all past a size guard. Diffs only
apply to completed `update` ops; rewrites still show full code.
https://claude.ai/code/session_01Rjkw1ST1UnrhyED9pghCui
* Add PR screenshots (temporary commit, reverted right after)
These images exist only so the PR description can embed them via
SHA-pinned raw URLs; the follow-up revert keeps them out of the tree.
https://claude.ai/code/session_01Rjkw1ST1UnrhyED9pghCui
* Revert temporary screenshot commit
https://claude.ai/code/session_01Rjkw1ST1UnrhyED9pghCui
---------
Co-authored-by: Claude <noreply@anthropic.com>
