feat(agent-manager): add PR panel refresh button

[marius-kilocode]

What Problem This Solves

The Agent Manager PR panel has no direct way to request fresh state while it remains open.

Why This Change Was Made

Reuse the existing cache-bypassing PR refresh request, scoped to the selected project and worktree. This keeps polling, GitHub HTTPS requests, and TLS verification unchanged. Unchanged results still avoid redundant UI updates after fetching.

User Impact

A Refresh icon now appears beside the existing PR header actions. It uses the shared small ghost button style, translated tooltip, and accessible label. Refresh keeps the panel and comments visible.

Evidence

• 44 focused tests pass, including correctly scoped refresh requests with and without a project ID, panel preservation, and updated PR title rendering.
• Extension compile, extension and webview typechecks, lint, formatting, knip, and the kilocode-change guard pass.
• Isolated VS Code verification covered the button style, Refresh tooltip, and clicking without closing the panel or hiding comments. This used fixture data, not an end-to-end live GitHub fetch.
• Manual check: open a real worktree PR, click Refresh, and confirm updated checks or comments appear without closing the panel.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (4 files)

• .changeset/agent-manager-pr-refresh.md
• packages/kilo-vscode/tests/fixtures/pr-comments-render.tsx
• packages/kilo-vscode/webview-ui/agent-manager/pr/PRPanel.tsx
• packages/kilo-vscode/webview-ui/agent-manager/pr/PRPanelHost.tsx

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_{Reviewed by grok-4.6 · Input: 70.3K · Output: 9.5K · Cached: 488.4K}

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