feat(ai): styles and strings for tool card piles, copy, failure tag, scroll button

[abose]

Summary

Styles and strings for the AI chat tool card piles and related polish. The behaviour lives in the companion phoenix-pro PR.

• Pile card: stacked-edges header, icon row, "N steps" label with a bump when a card lands, "N failed" note, read-files second line.
• Ghost fold animation overlay, kept outside the scroll container so it never changes the scroll height.
• Renders the five newest messages without the content-visibility intrinsic-size placeholder, which made every appended message occupy 300px for one frame and jolt a bottom-pinned list.
• Failed card accent and tag; capped, scrollable text detail with the thumb shown while hovering the panel; Copy button on expanded cards; truncation note for restored detail.
• Floating scroll-to-bottom button.
• New strings: pile steps, failed count, read files, more, failed tag, truncation note, scroll to bottom.

Test plan

• Lint hook on commit.
• Verified live in the desktop app together with the phoenix-pro PR.

🤖 Generated with Claude Code

https://claude.ai/code/session_01W8mue4oH8uExCg31KQW39p

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud