fix(vscode): support reactions on PR comment replies

[marius-kilocode]

What Problem This Solves

Agent Manager only rendered reaction controls for the root review comment. Reply IDs and reaction metadata were discarded, so replies could not be liked and their timestamps were missing.

Why This Change Was Made

Preserve GitHub reply metadata, authorize reply IDs in the reaction bridge, and render one reaction row per comment or reply. Root reactions now sit below the root body, matching GitHub thread layout. This is a follow-up to #13904.

User Impact

Users can react to every review-thread comment in the PR panel and inline diff view. Reply timestamps, existing reaction counts, and per-reply errors are shown correctly.

Evidence

• bun test tests/unit/am-pr-utils.test.ts tests/unit/am-pr-status-bridge.test.ts tests/unit/pr-comments-render.test.ts
• bun run check-types
• bun run check-types:webview
• bun run lint
• bun run bundle
• Storybook PR-panel screenshots were captured at wide and narrow widths.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (12 files)

• .changeset/pr-comment-reply-reactions.md
• packages/kilo-vscode/src/agent-manager/pr-status-bridge.ts
• packages/kilo-vscode/src/agent-manager/pr/am-pr-utils.ts
• packages/kilo-vscode/tests/fixtures/pr-comments-render.tsx
• packages/kilo-vscode/tests/unit/am-pr-status-bridge.test.ts
• packages/kilo-vscode/tests/unit/am-pr-utils.test.ts
• packages/kilo-vscode/webview-ui/agent-manager/pr/PRCommentCard.tsx
• packages/kilo-vscode/webview-ui/agent-manager/pr/PRComments.tsx
• packages/kilo-vscode/webview-ui/agent-manager/pr/pr-panel.css
• packages/kilo-vscode/webview-ui/agent-manager/pr/pr-types.ts
• packages/kilo-vscode/webview-ui/diff-viewer/remote-comment-renderer.tsx
• packages/kilo-vscode/webview-ui/src/stories/agent-manager.stories.tsx

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_{Reviewed by grok-4.6 · Input: 207.1K · Output: 14.6K · Cached: 644.2K}

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