feat(ui): render the page toast from the status store

ShellFeedback and the scene director show toasts through createToast(),
each on its own timer as before, and the scene chrome renders the toast.
Every show rewrites the text, so a repeated message is announced again.

docs/VUE-MIGRATION.md

@@ -147,7 +147,9 @@ a feature supplying only its accent.
    (the top-center loading status and the road network and camera grid
    chips render what ShellFeedback and CctvControls publish to the
    `gev-status` store; `SplitFlapText` plays the departure-board flip that
-   `splitFlap.js` plans, writing only the label's one text node), then
+   `splitFlap.js` plans, writing only the label's one text node; the toast
+   renders what each owner's `createToast()` publishes there, on that
+   owner's own timer), then
    Cockpit (in progress: `CockpitBriefing` renders the briefing card's
    pages, cycle toggle, regional news and local conditions, and
    `CockpitContext` the Contact card's scope, navigation, counts, nearest