fix(ui-tui): clear sticky prompt when follow snaps to bottom

Renderer-driven follow-to-bottom was restoring the viewport to the tail without notifying ScrollBox subscribers, so StickyPromptTracker could stay stale-visible. Notify on render-time scroll/sticky changes and treat near-bottom as bottom for prompt hiding.

ui-tui/packages/hermes-ink/src/ink/components/ScrollBox.tsx

@@ -257,6 +257,7 @@ function ScrollBox({ children, ref, stickyScroll, ...style }: PropsWithChildren<
 
         if (el) {
           el.scrollTop ??= 0
+          el.notifyScrollChange = notify
         }
       }}
       style={{

ui-tui/packages/hermes-ink/src/ink/dom.ts

@@ -72,6 +72,7 @@ export type DOMElement = {
   scrollViewportHeight?: number
   scrollViewportTop?: number
   stickyScroll?: boolean
+  notifyScrollChange?: () => void
   // Set by ScrollBox.scrollToElement; render-node-to-output reads
   // el.yogaNode.getComputedTop() (FRESH — same Yoga pass as scrollHeight)
   // and sets scrollTop = top + offset, then clears this. Unlike an

ui-tui/packages/hermes-ink/src/ink/render-node-to-output.ts

@@ -761,6 +761,7 @@ function renderNodeToOutput(
         // active text selection by the same delta (native terminal behavior:
         // view keeps scrolling, highlight walks up with the text).
         const scrollTopBeforeFollow = node.scrollTop ?? 0
+        const stickyBeforeFollow = node.stickyScroll
 
         const sticky = node.stickyScroll ?? Boolean(node.attributes['stickyScroll'])
 
@@ -863,6 +864,10 @@ function renderNodeToOutput(
           scrollDrainNode = node
         }
 
+        if ((node.scrollTop ?? 0) !== scrollTopBeforeFollow || node.stickyScroll !== stickyBeforeFollow) {
+          node.notifyScrollChange?.()
+        }
+
         scrollTop = clamped
 
         if (content && contentYoga) {

ui-tui/src/components/appChrome.tsx

@@ -256,15 +256,21 @@ export function StickyPromptTracker({ messages, offsets, scrollRef, onChange }:
       }
 
       const top = Math.max(0, s.getScrollTop() + s.getPendingDelta())
+      const vp = Math.max(0, s.getViewportHeight())
+      const total = Math.max(vp, s.getScrollHeight())
+      const atBottom = s.isSticky() || top + vp >= total - 2
 
-      return s.isSticky() ? -1 - top : top
+      return atBottom ? -1 - top : top
     },
     () => NaN
   )
 
   const s = scrollRef.current
   const top = Math.max(0, (s?.getScrollTop() ?? 0) + (s?.getPendingDelta() ?? 0))
-  const text = stickyPromptFromViewport(messages, offsets, top, s?.isSticky() ?? true)
+  const vp = Math.max(0, s?.getViewportHeight() ?? 0)
+  const total = Math.max(vp, s?.getScrollHeight() ?? vp)
+  const atBottom = (s?.isSticky() ?? true) || top + vp >= total - 2
+  const text = stickyPromptFromViewport(messages, offsets, top, atBottom)
 
   useEffect(() => onChange(text), [onChange, text])