Add App Store screenshot harness + listing metadata

DEBUG-only screenshot support (seeded sample data via ScreenshotSeed, per-screen
launch args, screenshot roots for both apps) so iPhone + Apple Watch App Store
shots can be captured deterministically from the simulator — all excluded from
release builds. Also seed ExerciseView's set-grid progress in init so it renders
correctly on the first frame. Adds Scripts/metadata/ as the listing source of
truth (copy, URLs, review notes, and the captured screenshots).

Claude-Session: https://claude.ai/code/session_018gg69MaUetDNzWzBXisfMV

Workouts/WorkoutsApp.swift

@@ -14,11 +14,23 @@ struct WorkoutsApp: App {
 
     var body: some Scene {
         WindowGroup {
-            RootGateView()
-                .environment(services)
-                .environment(services.syncEngine)
-                .modelContainer(services.container)
-                .task { await services.bootstrap() }
+            #if DEBUG
+            if ScreenshotSeed.isActive {
+                ScreenshotRootView(services: services)
+            } else {
+                root
+            }
+            #else
+            root
+            #endif
         }
     }
+
+    private var root: some View {
+        RootGateView()
+            .environment(services)
+            .environment(services.syncEngine)
+            .modelContainer(services.container)
+            .task { await services.bootstrap() }
+    }
 }