feat(quick-25): create useVideoAutoplay hook

- Manages video play/pause based on hover and selection state
- 300ms hover delay before playing, immediate play on selection
- Pauses on mouse leave or deselection (resumes from position)
- Catches AbortError from interrupted play() promises

src/hooks/useVideoAutoplay.ts

@@ -0,0 +1,76 @@
+import { useRef, useEffect } from "react";
+import { useWorkflowStore } from "@/store/workflowStore";
+
+/**
+ * Hook for managing video play/pause based on hover and selection state.
+ *
+ * Videos are paused by default. They start playing when:
+ * - The node is selected (immediately)
+ * - The node is hovered for 300ms (delayed)
+ *
+ * Videos pause when:
+ * - The node is deselected (if not hovered)
+ * - The mouse leaves the node (if not selected)
+ *
+ * @param nodeId - The node's unique ID
+ * @param selected - Whether the node is currently selected
+ * @returns A ref to attach to the video element
+ */
+export function useVideoAutoplay(
+  nodeId: string,
+  selected: boolean | undefined
+): React.RefObject<HTMLVideoElement | null> {
+  const videoRef = useRef<HTMLVideoElement | null>(null);
+  const hoverTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const hoveredNodeId = useWorkflowStore((s) => s.hoveredNodeId);
+
+  const isHovered = hoveredNodeId === nodeId;
+
+  useEffect(() => {
+    const video = videoRef.current;
+    if (!video) return;
+
+    // Clear any pending hover timeout
+    const clearHoverTimeout = () => {
+      if (hoverTimeoutRef.current) {
+        clearTimeout(hoverTimeoutRef.current);
+        hoverTimeoutRef.current = null;
+      }
+    };
+
+    if (selected || isHovered) {
+      // Play the video
+      if (selected) {
+        // Selected: play immediately
+        clearHoverTimeout();
+        video.play().catch((e) => {
+          if (e.name !== "AbortError") {
+            console.warn("Video play failed:", e);
+          }
+        });
+      } else if (isHovered) {
+        // Hovered but not selected: play after 300ms delay
+        clearHoverTimeout();
+        hoverTimeoutRef.current = setTimeout(() => {
+          video.play().catch((e) => {
+            if (e.name !== "AbortError") {
+              console.warn("Video play failed:", e);
+            }
+          });
+        }, 300);
+      }
+    } else {
+      // Not selected and not hovered: pause
+      clearHoverTimeout();
+      video.pause();
+      // Note: Do NOT reset currentTime - resume from current position
+    }
+
+    // Cleanup on unmount or dependency change
+    return () => {
+      clearHoverTimeout();
+    };
+  }, [isHovered, selected, nodeId]);
+
+  return videoRef;
+}