fix(ui): add subtask stop controls

[kilo-code-bot]

Summary

• Adds a stop action to running subtask tool rows so child sessions can be aborted independently.
• Wires the VS Code webview DataProvider to abort a specific session instead of only the active chat session.
• Adds a reusable BasicTool action slot for inline tool controls.

Fixes #7862

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (7 files)

• packages/kilo-ui/src/components/basic-tool.css
• packages/kilo-ui/src/components/message-part.tsx
• packages/kilo-vscode/webview-ui/src/App.tsx
• packages/kilo-vscode/webview-ui/src/context/session.tsx
• packages/ui/src/components/basic-tool.css
• packages/ui/src/components/basic-tool.tsx
• packages/ui/src/context/data.tsx

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_{Reviewed by gpt-5.4-20260305 · 719,265 tokens}