Implement session outcomes, step timing, and live timer fixes

frontend/src/hooks/useSessionTimer.ts

@@ -5,12 +5,23 @@ export function useSessionTimer(startedAt: string | undefined | null): string |
   const intervalRef = useRef<ReturnType<typeof setInterval> | null>(null)
 
   useEffect(() => {
+    // Always clear any previous interval before (re)initializing.
+    if (intervalRef.current) {
+      clearInterval(intervalRef.current)
+      intervalRef.current = null
+    }
+
     if (!startedAt) {
       setElapsed(null)
       return
     }
 
-    const startTime = new Date(startedAt).getTime()
+    const parsedStartTime = new Date(startedAt).getTime()
+    // If the server timestamp is invalid or ahead of the local clock, fall back to "now"
+    // so the timer still starts ticking immediately for the user.
+    const startTime = Number.isNaN(parsedStartTime) || parsedStartTime > Date.now()
+      ? Date.now()
+      : parsedStartTime
 
     const tick = () => {
       const diff = Math.max(0, Math.floor((Date.now() - startTime) / 1000))