One-shot Playwright probe that drives the live Toast demo, installs a
MutationObserver on the toast item, clicks dismiss, and reports the full
attribute timeline.
Used to confirm that `runtime.trigger('dismiss')` actually fires the
`data-event*` perceptual signal in the browser. The signal lives ~13ms
in the DOM (1 awaited rAF + 1 hold frame + cleanup), which is too brief
for DevTools' attribute panel to refresh — this probe captures the full
sequence with millisecond timestamps so the contract is observable.
Run:
1. `npm run dev`
2. `node --import tsx/esm scripts/probe-toast-dismiss.ts`
Output ends with "Signal observed: ✅ YES" when the runtime is wired
correctly. Useful as a regression probe after touching the trigger
sequence or the Toast wiring.
