[ui] break down SessionDetail.tsx into focused components

[duonghb53]

Context

Port of upstream agent-orchestrator PR #1449 — refactor(web): break down SessionDetail.tsx into focused components.

Upstream SessionDetail.tsx was ~900 lines. Decomposed into:

• SessionDetailHeader.tsx
• SessionDetailPRCard.tsx
• SessionEndedSummary.tsx
• PRCommentThread.tsx

Result: easier review, isolated tests, fewer rerender cascades.

Files (ao-rs)

• crates/ao-desktop/ui/src/components/SessionDetail.tsx — currently the catch-all

Changes

1. Audit current SessionDetail.tsx line count + responsibilities.
2. Extract:
   • Header (title, status pills, top-bar actions)
   • PR card (PR state, CI, review decision, merge actions)
   • Ended summary (terminated + summary view)
   • Comment thread (review comments / bugbot list, if applicable)
3. Each new component owns its own test file.
4. No behavior change — purely structural.

Acceptance

• SessionDetail.tsx ≤ ~200 lines orchestration only.
• Visual + behavior unchanged in dashboard.
• Per-component tests added.