[BUG] Desktop App: caret can't be placed inside text in a detached session window (Open in → New window) — typed text appends to end of block

Bug

In the Claude Code Desktop App, when a session is opened in a separate window via right-click session → Open in → New window, the text caret cannot be positioned inside a block of text. Clicking anywhere within a paragraph does not place the caret at the click location — instead, any typed characters are always appended to the end of the entire block.

This works correctly in the normal in-app session window.

Repro

1. Open the Claude Code Desktop App.
2. Right-click a session → Open in → New window.
3. In that new window, place a multi-line block of text, e.g.:

```
Health

Any reason you shouldn't do physical activity? (Yes/No + details)
Most recent ECG (date), Most recent blood tests (date)
Asthma? (Yes/No + which)
```

1. Click at the end of the first question line and type NO.

Expected (and how it works in the normal in-app window) ✅

The caret lands where you clicked and the text inserts inline:

Health

Any reason you shouldn't do physical activity? (Yes/No + details) NO
Most recent ECG (date), Most recent blood tests (date)
Asthma? (Yes/No + which)

Actual (in the "New window") ❌

No matter where you click in the paragraph, the caret won't land there — the typed NO is dumped at the very bottom, after the whole block:

Health

Any reason you shouldn't do physical activity? (Yes/No + details)
Most recent ECG (date), Most recent blood tests (date)
Asthma? (Yes/No + which)
 NO

Impact

Makes it impossible to fill in a template/form inline (answering questions in place) within a detached session window.

Environment

• Claude Code Desktop App
• macOS (Darwin 25.5.0)