Redesign Classic layout for desktop and mobile

PRODUCT.md

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+# YT Player
+
+<!-- impeccable:product-schema 1 -->
+
+## Platform
+
+web
+
+## Users
+
+People watching videos and listening to music on desktop and mobile. The confirmed Classic brief gives watching and listening equal priority.
+
+## Product Purpose
+
+Search and play YouTube media, organize playlists, and keep saved media available offline. The web PWA and desktop wrappers share the same frontend.
+
+## Capabilities and Constraints
+
+Preserve playback, playlists, queue, lyrics, notes, A–B loops, audio-only mode, offline storage, sharing, and settings. The frontend is plain HTML, CSS, and JavaScript with a Bun/Hono web backend. Classic is the default layout; other layouts share markup and must retain their behavior. Appearance settings include dark, light, contrast, font scale, density, performance, and reduced motion.
+
+## Brand Commitments
+
+Keep the YT Player name and existing factual copy. The approved Classic redesign uses a quiet dark studio direction. Other layout themes remain independent.
+
+## Evidence on Hand
+
+Existing frontend, bundled fonts, local icons, and browser tests. No invented customer claims or production data.
+
+## Product Principles
+
+- Playback and browsing must remain reachable together.
+- Mobile browser and installed PWA should offer consistent Classic navigation.
+- Empty, populated, and playing states each need an appropriate layout.
+- User data and appearance preferences survive theme changes.