fix(vscode): prevent shell output from blanking webview

[marius-kilocode]

Agent Manager can turn into a blank gray editor after expanding a completed Shell tool call in a large session. The failure was reproduced by opening a long Agent Manager transcript, expanding a Shell output pane, and observing the webview stop painting while Agent Manager extension-host polling continued. Because the renderer fails below the application JavaScript, the webview console may show no exception.

The polished Shell preview from #11146 renders the command and output as Shiki-highlighted DOM. Its final restore-motion commit also enabled BasicTool content-height animation for Shell. BasicTool animates the details region from 0px to auto. For a large highlighted output, Chromium repeatedly recalculates and lays out the full Shiki span tree and surrounding transcript during the animation. In an already large Agent Manager session, that layout pressure can make the webview renderer unresponsive, leaving only VS Code's gray webview background.

Disable the content-height animation for Shell only. The command and output remain highlighted, copy and open-in-editor controls remain available, and the chevron still animates. Other tool previews retain their existing motion.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (4 files)

• .changeset/steady-shell-expansion.md
• packages/kilo-docs/public/img/screenshot-tests/kilo-vscode/visual-regression/agentmanager/diff-panel-with-diffs-chromium-linux.png
• packages/kilo-ui/src/components/message-part.tsx
• packages/kilo-vscode/tests/unit/kilo-ui-contract.test.ts

The fix is minimal and targeted: removing the animated prop from the bash BasicTool registration disables the content-height animation that was driving layout thrash on large Shiki-highlighted shell outputs. The contract test was updated to assert the animation is absent (allowPendingToggle no longer followed by animated), and the updated visual-regression baseline is consistent with the behavior change. The chevron and other tool previews retain their existing motion.

Previous Review Summary

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review

Status: No Issues Found | Recommendation: Merge

Files Reviewed (3 files)

• .changeset/steady-shell-expansion.md
• packages/kilo-ui/src/components/message-part.tsx
• packages/kilo-vscode/tests/unit/kilo-ui-contract.test.ts

---

_{Reviewed by glm-5.2-20260616 · 219,154 tokens}

_{Review guidance: REVIEW.md from base branch main}