fix(ui): hold info toast ~1s before it rises and fades

The info toast began drifting up and fading the instant it finished
appearing (the CSS keyframes went straight from the 12% appeared-stop to
the 100% risen-and-faded stop), so a glanced message was already leaving.

Insert a ~1s hold at full opacity/rest before the rise-and-fade: extend the
animation 2s → 3s with keyframe stops at 8% (appeared, ~240ms) and 41% (end
of the ~1s hold), keeping the original rise-and-fade pace for the tail. The
reduced-motion variant gets the same appear/hold/fade timing (fade only, no
travel). The showToast dismissal timer is bumped 2000 → 3000ms to stay in
lockstep with the animation (the error toast's 4s dwell is unchanged).

ui/src/lib/app.svelte.ts

@@ -214,9 +214,9 @@ function goForeground(): void {
 export function showToast(text: string, kind: Toast['kind'] = 'info'): void {
   app.toast = { kind, text, seq: ++toastSeq };
   if (toastTimer) clearTimeout(toastTimer);
-  // An info bubble lives exactly as long as its rise-and-fade animation (2s); an error
-  // dwells longer (4s) so it is not missed.
-  toastTimer = setTimeout(() => (app.toast = null), kind === 'error' ? 4000 : 2000);
+  // An info bubble lives exactly as long as its appear + ~1s hold + rise-and-fade animation (3s);
+  // an error dwells longer (4s) so it is not missed.
+  toastTimer = setTimeout(() => (app.toast = null), kind === 'error' ? 4000 : 3000);
 }
 
 /** dismissToast hides the current toast at once — a tap on the bubble dismisses it. */