fix(app): audio pipeline stability, cookie login, discovery filtering, and feed performance

[ajisth69]

Overview

Comprehensive update resolving audio pipeline stability, YouTube Music authentication, Discovery recommendation quality, Feed queue behavior, and Feed loading performance.

---

1. Discovery Recommendation Engine

• Exclude Listened Tracks: Added isAlreadyListened filtering in DiscoverRepository checking across user history (recentTracksRaw, topTracksRaw, ytMusicRecentRaw, ytMusicLikedRaw, ytMusicFeedRaw, and saved playlist keys) by key and normalized artist|title.
• Prevent Artist Clumping: Set DISCOVER_ARTIST_CAP = 1 (was 3) so batches do not repeatedly surface the same artist.
• Removed Raw History Injection: Stopped feeding 40 ytMusicFeedRaw listening history tracks directly into discover candidates.
• Instant Display: Cached discover tracks render immediately on screen open to prevent empty shimmer state.

2. Smart Feed Queues & Radio Continuation

• Context-Aware Radio on Single Track Click: Tapping an individual track in Quick Picks, Because you listen to, Fresh Finds, or Charts now calls viewModel.playTrack(track, ..., startRadio = true). This generates an intelligent 25+ track context-aware radio queue instead of playing a static 5–10 track slice.
• Endless Queue for "Play All" / Shuffle: Updated playTracksQueue, shuffleTracksQueue, playRecentQueue, and playGeneratedQueue with enableRadioContinuation = true. When the queue nears its end, MusicPlayer continuously extends the queue with contextually related tracks.

3. Feed Performance & Balance

• Eliminated Blocking Network Calls: Removed 4 sequential fetchArtistPage calls in artistReleases (saving 2–4s per load), consuming matchedReleases directly from the parallel fetchNewReleases query.
• Artist Search Cache: Added in-memory artistEntityCache: ConcurrentHashMap<String, FeedArtist> in FeedRepository to avoid duplicate searchArtists calls across feed refreshes.
• Related Tracks Timeout: Guarded discoveryDef.await() with withTimeoutOrNull(3000L) to prevent slow graph queries from holding up feed rendering.
• Balanced Quick Picks: Boosted fresh trending tracks and charts alongside personal picks, interleaving familiar tracks with discoveries so the feed is not dominated by past listening history.
• Instant Feed Display: Cached feed data is emitted immediately on connection updates in FeedViewModel without waiting for network reloads.

4. YouTube Music Cookie Login (Matching Desktop)

• Added CookieNormalizer.kt (direct port of Desktop InnerTubeMusicApi.normalizeCookies): supports raw Cookie headers, Netscape cookies.txt format, JSON exports from browser extensions (Cookie-Editor, EditThisCookie), and multiline text.
• Added CookieLoginDialog.kt with clipboard paste helper, real-time validation error alerts, and seamless connection.
• Integrated Cookie Login into both YouTubeLoginScreen.kt and SettingsScreen.kt.
• Added unit tests in CookieNormalizerTest.kt.

5. Audio Pipeline & Bit-Perfect Playback

• Crossfade Audio Focus: Fixed pause loop in handOffCrossfade() by keeping handleAudioFocus = false on the standby player so ExoPlayer doesn't fight LastWave's manual focus management.
• Poweramp Bit-Perfect Definition Alignment: Updated SignalPath.kt so software gain override does not disqualify bit-perfect mode when sample rate and bit depth match the DAC wire format.
• Poweramp-Style Signal Path Redesign: Reorganized the Output Detector dialog into Poweramp's 5-stage top-to-bottom pipeline flow (Source $\to$ DSP $\to$ Volume Control $\to$ Output $\to$ Output Device) with status cards.
• DAC Stability: Reverted forceSoftwareVolume default to false and guarded against ReadOnlyBufferException crashes on read-only MediaCodec buffers.