Pop out window renders too small in Safari (title bar height eats into content area)

Nobody has claimed this yet.

The pop out window renders noticeably smaller in Safari than it does in Firefox. It looks like the difference is that Firefox doesn't include the height of the title bar in the window open size but Safari does.

## Repro Steps

1. Open one.livesplit.org in both Firefox and Safari.
2. Load the same splits/layout in both.
3. Click "Pop Out" in both.

## Expected behavior

The pop-out window's content should render at roughly the same size in both browsers, matching the size of the main window's splits view.

## Actual behavior

In Safari, the pop-out window's content (text, rows, header) is noticeably smaller than in Firefox — see attached screenshot (Firefox on the left, Safari on the right, same splits/layout). I believe this is because in Firefox the content size is the same as the content size from the main window but in Safari it's the full window size that matches, reducing the content size by the height of the title bar.

## Environment

- macOS 26.6.2 (25G83)
- Safari 26.6.2 (21624.5.1.11.3)
- Firefox 154.0.1

Start by locating the Pop Out entry point and the code that calculates the new window size. Reproduce the issue in Safari and Firefox with the same splits and layout, then verify that the pop-out content area is the same size as the main window's splits view in both browsers.

Written by the indexing model from the issue text.