fix(table): typewriter prevText in state, not ref (concurrent-render flash)

The render-phase reset used a ref (prevTextRef) for change detection. Under
React 18 concurrent rendering, a render can be started then discarded; the
ref mutation survives but the setRevealed('') rolls back. The committed render
then sees prevTextRef === text, skips the reset, and `revealed ?? kind.text`
paints the full value for one frame before the animation overwrites it —
an intermittent full-text flash during runs with many streaming cells.

Track the previous text in state so it rolls back with the discarded render
and the reset re-fires on the committed one. Also guard the animation effect
against a null/empty text (stale animateRef from a discarded render).

Author: TheodoreSpeaks

apps/sim/app/workspace/[workspaceId]/tables/[tableId]/components/table-grid/cells/cell-render.tsx

@@ -303,15 +303,21 @@ const TYPEWRITER_MS_PER_CHAR = 15
  */
 function useTypewriter(text: string | null): string | null {
   const [revealed, setRevealed] = useState<string | null>(text)
-  const prevTextRef = useRef<string | null>(text)
+  // Track the previous text in STATE, not a ref. The reset below runs during
+  // render; under concurrent rendering React can start a render, mutate a ref,
+  // then discard that render. A ref keeps the mutation, so the committed render
+  // sees prevText === text, skips the reset, and `revealed ?? kind.text` flashes
+  // the full value for a frame. State rolls back with the discarded render, so
+  // the reset re-fires on the committed one.
+  const [prevText, setPrevText] = useState<string | null>(text)
   const mountedRef = useRef(false)
   const animateRef = useRef(false)
 
   // Reset synchronously during render when `text` changes (not on first mount)
   // so no frame ever shows the full new value before the animation begins —
   // an effect-based reset lands one frame late and flashes the whole text.
-  if (prevTextRef.current !== text) {
-    prevTextRef.current = text
+  if (prevText !== text) {
+    setPrevText(text)
     const animate = mountedRef.current && text !== null && text.length > 0
     animateRef.current = animate
     setRevealed(animate ? '' : text)
@@ -322,9 +328,9 @@ function useTypewriter(text: string | null): string | null {
   }, [])
 
   useEffect(() => {
-    if (!animateRef.current) return
+    if (!animateRef.current || text === null || text.length === 0) return
     animateRef.current = false
-    const full = text as string
+    const full = text
     const start = performance.now()
     let raf = 0
     const tick = (now: number) => {