[Bug]: Right panel width too narrow when opening a browser (and other things) #23195

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/desktop

Steps to reproduce

1. Open T3 Code (nightly) on a large monitor.
2. Start a new agent thread.
3. Open a side panel for a browser, either by clicking a URL or opening the side panel manually.

Expected behavior

I expect the side panel to either be much wider than it is, perhaps by assuming 50% width of the chat panel, or by remembering the width from the last time I opened the side panel.

Actual behavior

The side panel width is much more narrow than is reasonable, especially for diffs, PRs, and browser previews.

Here it is on a 5K 27" iMac:

This seems to be a recent regression, but I'm not sure exactly when it started.

Impact

Major degradation or frequent failure

Version or commit

Version 0.1.2-nightly.20261021.3499 (b5a226e)

Environment

macOS 26.6.2

Logs or stack traces

Screenshots, recordings, or supporting files

No response

Workaround

I have to resize the panel for every new agent thread, which gets very annoying.

This is most annoying on a large monitor, but less annoying on a smaller screen, like a laptop, probably because the panel width is fixed by pixels.