fix(timeline): use empty-deps useLayoutEffect for mount scroll to today

The guard-ref approach broke in React Strict Mode (dev): the ref
persisted as `true` across the simulated remount, so the second
invocation skipped the scroll — leaving scrollLeft=0 (today-90
at the left edge, not today). An empty-deps useLayoutEffect runs
twice in Strict Mode but both executions fire against the same
initial `toLeft` and produce the correct result.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/src/components/timeline/TimelineView.tsx

@@ -689,17 +689,15 @@ function TimelineViewContent({
   const pendingLeftCompensationPx = useRef(0);
   // Flag: scroll viewport to today after the next viewStart-driven re-layout.
   const pendingScrollToTodayRef = useRef(false);
-  // Guard: only auto-scroll to today once on initial mount.
-  const scrolledToTodayOnMount = useRef(false);
 
-  // Scroll to today on first mount so the viewport opens with today at the left edge.
+  // Scroll to today on mount so the viewport opens with today at the left edge.
+  // Empty deps: intentionally runs once (and twice in React Strict Mode dev, both correct).
+
   useLayoutEffect(() => {
-    if (scrolledToTodayOnMount.current) return;
     const el = scrollContainerRef.current;
     if (!el) return;
     el.scrollLeft = toLeft(today);
-    scrolledToTodayOnMount.current = true;
-  }, [toLeft, today]);
+  }, []);
 
   // Apply scroll compensation synchronously after the canvas grows (left-extend or Today button).
   useLayoutEffect(() => {