fix(ui): harden large-paste toast for mobile and stale state

Scope toast width overrides to sm+ so Sonner keeps full-width mobile
toasts, resolve ask actions from live composer/attachment state, and
extract offer-id invalidation into a unit-tested helper.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/components/chat/composer/largeTextPasteOffer.ts

@@ -0,0 +1,33 @@
+/**
+ * Offer-id state for the large-text paste ask toast.
+ *
+ * The toast can outlive the paste event (duration Infinity), and a second
+ * large paste can supersede an unanswered offer. These helpers keep that
+ * invalidation pure so ChatInput only wires toast UI to attach/inline actions.
+ */
+
+export type LargeTextPasteOfferAction = 'attach' | 'inline';
+
+/** Allocate a new offer id, superseding any unanswered previous offer. */
+export const beginLargeTextPasteOffer = (activeOfferId: number): number => (
+  activeOfferId + 1
+);
+
+/**
+ * Attempt to resolve an offer. Returns whether this call won the race, and the
+ * next active id. A superseded or already-resolved offer is rejected so
+ * dismiss/action cannot double-apply.
+ */
+export const resolveLargeTextPasteOffer = (
+  activeOfferId: number,
+  offerId: number,
+): { accepted: boolean; nextOfferId: number } => {
+  if (offerId !== activeOfferId) {
+    return { accepted: false, nextOfferId: activeOfferId };
+  }
+  return { accepted: true, nextOfferId: activeOfferId + 1 };
+};
+
+/** Toast chrome: widen on desktop only; leave mobile full-width to Sonner. */
+export const LARGE_TEXT_PASTE_TOAST_CLASSNAME =
+  '[&_[data-icon]]:!hidden sm:!min-w-[22rem] sm:!w-auto';