Root cause: extension service worker starts before Bun.serve() is
listening. First checkHealth() fails, next attempt is 10 seconds
later. User stares at "Connecting..." for 10 seconds.
Fix: retry every 1s for up to 15 attempts on startup, then switch
to 10s polling once connected (or after 15s gives up). Sidebar
should connect within 1-2 seconds of server becoming available.
3 new tests verify the fast-retry → slow-poll transition.
Garry Tan
d37e334f0d