[BUG] VS Code extension 2.1.270: live session tabs ignore the saved custom title and show the AI title (worked in 2.1.49)

**Summary:** In the VS Code extension 2.1.270, renaming a session tab is saved correctly to the transcript, but the tab of a **running** session keeps showing the auto-generated title instead. Sessions whose process is not alive show the custom name fine. This worked on 2.1.49.

**Steps to reproduce**
1. Open a session in the VS Code extension so its `claude` process is running.
2. Click the pencil icon on the tab, type a new name, press Enter.
3. The tab immediately shows the old AI-generated title again.
4. Close the tab (process exits) and reopen the session from history - the custom name is displayed correctly.

**Evidence on disk** - in `~/.claude/projects//.jsonl`, every rename is persisted, and each `custom-title` record is immediately followed by a stale `ai-title` record carrying the previous auto title:

```
262 {"type":"custom-title","customTitle":"","sessionId":""}
263 {"type":"ai-title","aiTitle":"","sessionId":""}
```

10 such pairs in one session - one per rename attempt. So the write path is fine; only the live tab rendering is wrong.

**Cross-check across four tabs in the same window** (process state from `ps`):

| session | process alive | tab displays | custom-title on disk |
|---|---|---|---|
| A | yes | AI title | present, ignored |
| B | yes | AI title | present, ignored |
| C | no | custom title | present, honoured |
| D | no | custom title | present, honoured |

Without exception: live process -> AI title wins; no live process -> custom title wins.

**Not a format change:** transcripts from 2026-08-16 and 2026-09-12, when live renaming worked, contain the exact same `custom-title` / `ai-title` interleaving. Only the live display behaviour changed.

**Expected:** once a session has a `custom-title`, it wins over `ai-title` in the tab, whether or not the session is running.

**Environment**
- VS Code extension: `anthropic.claude-code-2.1.270-darwin-arm64` (latest published)
- Previously installed: 2.1.49 (per `~/.vscode/extensions/.obsolete`), where renaming a live session worked
- macOS, Darwin 24.6.0, arm64

**Related:** #65010 (closed as inactive, now locked) reports the same symptom but attributes it to auto-retitling overwriting the stored name. Here the stored name survives - only the live tab ignores it.