[Bugs] Feature Request: PR state awareness in active sessions

**Mood:** 😔
**Category:** Bugs

Feature Request: PR state awareness in active sessions

When working in a project session, the agent has no awareness of GitHub events (PR merges, reviews, comment activity) on the PR it just created — even when the merge happens from within the Copilot app itself using the merge button in the top nav. The agent only knows the PR state if the user explicitly tells it or it queries via CLI.

What I'd expect: if I merge a PR from inside the Copilot app while in the session that created it, the agent should be notified — similar to how it gets notified when a background agent completes. At minimum, the session's tracked PR status should refresh so the agent knows it's merged without me having to tell it.

Why it matters: it breaks the conversational flow — the agent is still talking about a PR being "ready for review" after I've already merged it from the same app window.

---
| Field | Value |
| --- | --- |
| App version | 1.0.10 |
| OS | macOS 26.5.1 |
| Theme | GitHub |
| Path | /chat |
| Tenure | Week 4 |

从 /chat 会话流程开始，跟踪会话如何记录它创建的 PR，然后将其与 top-nav merge-button 流程以及现有的基于 CLI 的状态检查进行比较。完成的标准是：会话能够反映在应用内执行的 PR 合并，并且 agent 不再将已合并的 PR 报告为可供审核。

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