Fix Jump to Current button not appearing on scroll-up

The onScroll RAF optimization (only fire when atBottom changes) prevented
the button from showing because xterm's onScroll may not fire from wheel
events. Fix by setting isAtBottom(false) directly in the wheel handler
and removing the RAF guard to always schedule state updates.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/components/terminal/TerminalView.tsx

@@ -144,6 +144,8 @@ export default function TerminalView({ sessionId, active }: Props) {
       if (e.deltaY < 0) {
         autoFollowRef.current = false;
         setIsAutoFollow(false);
+        isAtBottomRef.current = false;
+        setIsAtBottom(false);
       }
     };
     containerRef.current.addEventListener("wheel", handleWheel, { capture: true, passive: true });
@@ -154,7 +156,6 @@ export default function TerminalView({ sessionId, active }: Props) {
     const scrollDisposable = term.onScroll(() => {
       const buf = term.buffer.active;
       const atBottom = buf.viewportY >= buf.baseY;
-      const prevAtBottom = isAtBottomRef.current;
       isAtBottomRef.current = atBottom;
 
       // Re-enable auto-follow only when USER scrolls to bottom (not write-triggered)
@@ -164,15 +165,12 @@ export default function TerminalView({ sessionId, active }: Props) {
         setIsAutoFollow(true);
       }
 
-      // Only update React state when value changes
-      if (atBottom !== prevAtBottom) {
       if (scrollStateRafId === null) {
         scrollStateRafId = requestAnimationFrame(() => {
           scrollStateRafId = null;
           setIsAtBottom(isAtBottomRef.current);
         });
       }
-      }
     });
 
     // Track text selection to show copy hint in status bar