Add game center, per-model shuffle, audio focus fixes, README, tests

- README.md with build/architecture overview
- Game Center screen with at-bat timeline, pitch sequence, spray chart,
  and strike zone component views
- VideoShuffle service: per-model bucketed random selection with
  no-back-to-back guarantee; replaces flat shuffle-bag approach
- Refresh JWT token for authenticated NSFW feed; add josie-hamming-2
  and dani-speegle-2 to the user list
- MultiStreamView audio focus: remove redundant isMuted writes during
  startStream and playNextWerkoutClip so audio stops ducking during
  clip transitions; gate AVAudioSession.setCategory(.playback) behind
  a one-shot flag
- GamesViewModel.attachPlayer: skip mute recalculation when the same
  player is re-attached (prevents toggle flicker on item replace)
- mlbTVOSTests target wired through project.yml with
  GENERATE_INFOPLIST_FILE; VideoShuffleTests covers groupByModel,
  pickRandomFromBuckets, real-distribution no-back-to-back invariant,
  and uniform model distribution over 6000 picks

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

project.yml

@@ -23,6 +23,17 @@ targets:
         CODE_SIGN_ENTITLEMENTS: mlbTVOS/mlbTVOS.entitlements
         PRODUCT_BUNDLE_IDENTIFIER: com.treyt.mlbTVOS
         SWIFT_STRICT_CONCURRENCY: complete
+  mlbTVOSTests:
+    type: bundle.unit-test
+    platform: tvOS
+    sources: [mlbTVOSTests]
+    dependencies:
+      - target: mlbTVOS
+    settings:
+      base:
+        PRODUCT_BUNDLE_IDENTIFIER: com.treyt.mlbTVOSTests
+        GENERATE_INFOPLIST_FILE: YES
+        SWIFT_STRICT_CONCURRENCY: complete
   mlbIOS:
     type: application
     platform: iOS