Support Firefox Container Tabs #28

Summary #

• browser.cookies.get without a storeId reads from the background context's default cookie store, so a margin_session cookie set inside a Firefox container tab was invisible to the extension and the popup stayed on the Sign In screen.
• getSessionCookie() now tries the active tab's cookieStoreId first, then the default store, then iterates cookies.getAllCookieStores() for the first match.

Test plan #

• In Firefox, log out of margin.at, then sign in to margin.at inside a container tab. Open the extension popup and confirm it shows the signed-in state.
• In a non-container tab, sign in and confirm the popup still works (regression check).

AI use disclosure #

AI was used to help diagnose the issue and propose the fix. The code has been manually reviewed and tested (there were no automated tests, none have been added).