P07: replace p7Step/p7UpdateDone with scripted beat system (beats 1-6)

Each beat reveals more content and shows a Next button or DemoArrow:
- Beat 1: msgs 1-4 (team planning) + Next → button
- Beat 2: msgs 1-9 (Lovable v1 card) + DemoArrow pointing to View Live Preview
- Beat 3: Stage View opens; rail msgs 1-12 (team feedback) + Next → in rail
- Beat 4: rail msgs 1-13 (In Progress card) + DemoArrow in rail
- Beat 5: update animation playing
- Beat 6: all messages revealed

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

Author: lambasu

src/components/ChatView.css

@@ -50,6 +50,22 @@
   flex-shrink: 0;
 }
 
+.p7-step-next {
+  flex-shrink: 0;
+  background: transparent;
+  border: 1px solid #b8860b;
+  color: #4a3000;
+  padding: 3px 10px;
+  border-radius: 4px;
+  cursor: pointer;
+  font-size: 12px;
+  font-weight: 600;
+  white-space: nowrap;
+}
+.p7-step-next:hover {
+  background: rgba(0,0,0,0.06);
+}
+
 
 /* Header styles live in ChatHeader.css. Compose styles live in Compose.css. */
 

src/components/StageView.css

@@ -250,6 +250,22 @@
   flex-shrink: 0;
 }
 
+.sv-rail-step-next-btn {
+  flex-shrink: 0;
+  background: transparent;
+  border: 1px solid #b8860b;
+  color: #4a3000;
+  padding: 2px 9px;
+  border-radius: 4px;
+  cursor: pointer;
+  font-size: 11px;
+  font-weight: 600;
+  white-space: nowrap;
+}
+.sv-rail-step-next-btn:hover {
+  background: rgba(0,0,0,0.06);
+}
+
 .sv-rail-messages {
   flex: 1;
   overflow-y: auto;

src/components/StageView.jsx

@@ -251,7 +251,6 @@ export default function StageView({ version = 'v1', onVersionChange, beat, onBea
   // It lags behind `version` to allow the update animation to play first.
   const [displayVersion, setDisplayVersion] = useState('v1')
   const [bannerState, setBannerState] = useState(null) // null | 'updating' | 'done'
-  const [updateComplete, setUpdateComplete] = useState(false)
   const prevVersionRef = useRef(version)
 
   useEffect(() => {
@@ -261,7 +260,6 @@ export default function StageView({ version = 'v1', onVersionChange, beat, onBea
       const applyTimer = setTimeout(() => {
         setDisplayVersion(version)
         setBannerState('done')
-        setUpdateComplete(true)
         onUpdateComplete?.()
         const clearTimer = setTimeout(() => setBannerState(null), 2200)
         return () => clearTimeout(clearTimer)