feat: demo control lingers — tour resumes after 5s of stillness

Leaving the tube no longer snaps the tour back: the pointer stays
parked where the visitor left it, and the tour only picks the loop
back up after five seconds without any interaction (same timer covers
going idle while still hovering). The shared motion values mean the
resumed tour springs off from the parked position.

Author: ripgrim

apps/web/src/components/layout/landing/demo-screen.tsx

@@ -528,16 +528,31 @@ export function DemoScreen() {
     )
   }, [])
 
-  // The tour runs itself until the visitor's mouse takes the screen; on leave
-  // it picks the loop back up from wherever they left it.
+  // The tour runs itself until the visitor's mouse takes the screen. Control
+  // is held for as long as they keep interacting; after 5s of stillness (or
+  // after leaving) the tour resumes — springing off from wherever the cursor
+  // was left, since the same motion values carry both modes.
   const [interactive, setInteractive] = useState(false)
   const [pressed, setPressed] = useState(false)
   const rootRef = useRef<HTMLDivElement>(null)
+  const idleTimer = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const touch = () => {
+    setInteractive(true)
+    if (idleTimer.current) clearTimeout(idleTimer.current)
+    idleTimer.current = setTimeout(() => setInteractive(false), 5000)
+  }
+  useEffect(
+    () => () => {
+      if (idleTimer.current) clearTimeout(idleTimer.current)
+    },
+    []
+  )
   const { scene, phase, next, goTo } = useTour(reduceMotion, interactive)
   const cursor = useDemoCursor(phase, next, scene, interactive)
 
   // Map the real pointer into the demo's 2× coordinate space.
   const onPointerMove = (e: React.PointerEvent) => {
+    touch()
     const rect = rootRef.current?.getBoundingClientRect()
     if (!rect) return
     cursor.x.set((e.clientX - rect.left) * 2)
@@ -549,13 +564,13 @@ export function DemoScreen() {
       ref={rootRef}
       className="h-full w-full overflow-hidden"
       style={{ background: P.bg, cursor: "none" }}
-      onPointerEnter={() => setInteractive(true)}
-      onPointerLeave={() => {
-        setInteractive(false)
-        setPressed(false)
-      }}
+      onPointerEnter={touch}
+      onPointerLeave={() => setPressed(false)}
       onPointerMove={onPointerMove}
-      onPointerDown={() => setPressed(true)}
+      onPointerDown={() => {
+        touch()
+        setPressed(true)
+      }}
       onPointerUp={() => setPressed(false)}
     >
       <div