fix(timeline): wait for canvas width before scrolling to today

useLayoutEffect([]) fired before isInitialLoading resolved, so the
scroll container had no canvas yet — scrollLeft was clipped to 0.
Now the scroll-to-today fires on the first render where totalCanvasWidth
becomes non-zero. The cleanup effect resets the guard on unmount so
React Strict Mode's fake-unmount+remount also scrolls correctly.

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

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

@@ -689,15 +689,25 @@ function TimelineViewContent({
   const pendingLeftCompensationPx = useRef(0);
   // Flag: scroll viewport to today after the next viewStart-driven re-layout.
   const pendingScrollToTodayRef = useRef(false);
-
-  // 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).
-
+  // Guard reset on every real unmount (including Strict Mode fake-unmount) so the
+  // scroll-to-today fires correctly on remount.
+  const hasScrolledToTodayOnLoad = useRef(false);
   useLayoutEffect(() => {
+    return () => {
+      hasScrolledToTodayOnLoad.current = false;
+    };
+  }, []);
+
+  // Scroll to today the first time the canvas has its full width (after initial data load).
+  // Depends on totalCanvasWidth so it fires after isInitialLoading → false renders the canvas.
+  useLayoutEffect(() => {
+    if (totalCanvasWidth === 0) return;
+    if (hasScrolledToTodayOnLoad.current) return;
     const el = scrollContainerRef.current;
     if (!el) return;
     el.scrollLeft = toLeft(today);
-  }, []);
+    hasScrolledToTodayOnLoad.current = true;
+  }, [totalCanvasWidth, toLeft, today]);
 
   // Apply scroll compensation synchronously after the canvas grows (left-extend or Today button).
   useLayoutEffect(() => {