"Open out-of-scope URLs in a default browser" not working for Google Messages on MacOS

### Description Until about FF 147, you could click a link from a text message in Google Messages and it would open in the MacOS default browser. Now, all links open in a new tab in the PWA instead, regardless of whether "Open out-of-scope URLs in a default browser" is checked in Settings. ### Steps to Reproduce <!-- Steps to reproduce this bug --> 1. Check the box for "Open out-of-scope URLs in a default browser" in Settings 2. Click a link in the PWA ### Additional Information Only tested with Google Messages PWA. Until about FF 147, the behavior worked as expected. FWIW, Google Messages using a Chrome PWA will also ignore the default browser, at least on Windows. Not sure if that behavior is impacting this. I'm less suspicious of that since it used to work as intended. ### Affected Websites * https://messages.google.com/web/conversations/ ### Environment * Operating system: MacOS Tahoe 26.3.1 * System architecture: M1 * Installation method: homebrew * PWAsForFirefox extension version: 2.18.0 * Firefox version: 148.0.2 I also have regular Firefox installed (148.0.2) but it's not the default browser.