fix(web): clean up review CSS and drop stale comment jumps

[tomasz-tomczyk]

Summary

Pre-release audit fixes for v0.21.0..main.

• Story file-level comments (.file-comments) are now left-aligned at a 16px inset. Before, they were centered while review-list diffs left-align them (feat(web): left-align file-level comments in diffs #1008). Only the story view builds .file-comments. The story e2e helper now checks the alignment.
• File header CSS: removed the .crit-review-file-header side borders and radius. After feat(web): border each file and use the code background for comment rows #1004, all three render paths (review list, story, theme preview) overrode them. top: 0 stays.
• Outdated-thread CSS: the rules now share selector lists with .pierre-file-level instead of repeating the four layout contexts. The reviewer checked that the computed values are unchanged.
• Comment jumps: each Pierre comment jump now gets a number. A jump that a newer one has replaced stops after loading, during the scroll-settle poll and before its callback. This stops the flicker on fast next-comment navigation.
• Comment: added a note on why diff jumps don't wait for the list scroll to settle. Pierre scrolls instantly, and waiting would add at least 250ms per step.

No vendored renderer modules were changed, so no crit-web sync is needed. crit-web has no story mode, so nothing needs porting. The related crit-web parity fix is in tomasz-tomczyk/crit-web#435.

Test plan

• npm run test:frontend (645 passed)
• eslint, stylelint, scripts/check-css-vars.sh
• Targeted e2e on git-mode (105 passed): pierre-settings, file-comments, comments-panel, story, comment-nav, folded-comment-nav, comment-ref-links, outdated-diff-comments, theme-preview
• CI green

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.51%. Comparing base (f52b934) to head (2fda4fa).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1011      +/-   ##
==========================================
+ Coverage   75.50%   77.51%   +2.01%     
==========================================
  Files         161      168       +7     
  Lines       23403    23545     +142     
==========================================
+ Hits        17671    18252     +581     
+ Misses       4325     3886     -439     
  Partials     1407     1407              

Flag	Coverage Δ
e2e	27.16% <ø> (?)
unit	75.51% <ø> (+<0.01%)	⬆️

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