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 Watch App/WatchAppServices.swift

@@ -15,6 +15,9 @@ final class WatchAppServices {
         let container = WorkoutsModelContainer.make()
         self.container = container
         self.bridge = WatchConnectivityBridge(container: container)
+        #if DEBUG
+        if ScreenshotSeed.isActive { ScreenshotSeed.populate(container.mainContext) }
+        #endif
     }
 
     func activate() {