fix(vscode): use native sandbox notifications

[marius-kilocode]

The sandbox toggle currently reports successful state changes inside the webview, unlike auto-approve and other VS Code-level mode changes. Its longer explanatory copy also makes a simple enabled or disabled transition harder to scan.

This moves successful sandbox feedback to native VS Code notifications with concise Sandbox enabled and Sandbox disabled messages. Detailed failure feedback remains in the webview, and native notifications are only emitted after a toggle completes successfully.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (6 files)

• .changeset/notify-sandbox-state.md
• packages/kilo-vscode/src/KiloProvider.ts
• packages/kilo-vscode/tests/setup/vscode-mock.ts
• packages/kilo-vscode/tests/unit/kilo-provider-load-messages.test.ts
• packages/kilo-vscode/tests/unit/prompt-input-connection-guard.test.ts
• packages/kilo-vscode/webview-ui/src/components/chat/PromptInput.tsx

---

_{Reviewed by gpt-5.4-2026-03-05 · Input: 243.4K · Output: 12.2K · Cached: 462.9K}

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