fix(vscode): preserve background agent spinner animation

[marius-kilocode]

What Problem This Solves

Expanded background-agent spinners restarted on every one-second job refresh. The shared spinner animation was correct, but the list used newly created agent objects as Solid list identities, replacing the rows and SVGs each time.

Why This Change Was Made

Key expanded rows by job ID and read current job data through a non-keyed Show, matching the existing collapsed preview. This preserves the spinner without changing shared animation styles or polling frequency. Titles, status, and row actions still use the latest snapshot.

User Impact

Background-agent spinners animate continuously while the list is expanded. Completed agents still show their final status and Dismiss control.

Evidence

• The browser regression failed before the fix because the first refresh detached the original SVG. It passes after the fix, including three repeated runs, and verifies updated titles and completion state.
• Extension compilation, host/webview typechecks, lint, 22 focused unit tests, both background-agent browser tests, Knip, and the change-marker guard pass.
• Isolated VS Code verification preserved the original SVGs and animation objects through four one-second refreshes. Completing one job updated its icon, status, and controls while the other spinner continued.
• UI verification used synthetic responses matched to real outgoing request IDs, with no model requests or credentials. Backend job execution was not tested. The screenshot shows the completion state; animation continuity was measured separately because screenshot capture temporarily disables animations.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (3 files)

• .changeset/smooth-background-agent-spinner.md
• packages/kilo-vscode/tests/accessibility.spec.ts
• packages/kilo-vscode/webview-ui/src/components/chat/BackgroundAgents.tsx

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[WebReflection]

nice way to enforce keys!