[schloerke]

Fixes posit-dev/shinyreact#328.

Root cause: Shiny fires shiny:connected, shiny:disconnected, shiny:busy, and shiny:idle with jQuery's trigger(). That only calls jQuery handlers; document.addEventListener() never sees them. The lifecycle store listened with addEventListener(), so:

• there was no way to see a disconnect (the issue), and
• useShinyBusy() never updated in a real browser either. Its unit tests passed because they send native events.

Changes:

• A small onShinyEvent() helper listens through window.jQuery(document).on() when jQuery is on the page, and falls back to addEventListener() otherwise. jQuery handlers also get native events, so the jsdom tests still work.
• The lifecycle store and the dependency-discovery shiny:connected wait both use it.
• New useShinyConnected() hook: false until the socket opens, false again on disconnect, true again if Shiny reconnects. It seeds from Shiny.shinyapp.isConnected() for late mounts. useShinyInitialized() is unchanged (it stays true).
• The hook is exported on window.shinyreact and the npm entry, and taught in the shinyreact-build-app skill.

Checked by hand in a browser with an R app: "Busy" now shows during a slow request, and stopping the R process flips the hook to false.