[Umangnamdeo]

Summary of Changes

This pull request addresses several stability, performance, and security issues across the desktop audio pipeline:

1. Security & Local Server Isolation (local_media_server.dart)

   • Enforced ephemeral authentication token verification on all loopback requests to prevent unauthorized local port scanning or stream interception.

2. Audio Hardware Fallback & Safety (wasapi_engine.dart)

   • Added bounded timeouts and exception handling around device probing and volume control to prevent driver hangs and unhandled platform exceptions.
   • Added format support validation before attempting exclusive mode handoffs.

3. Playback Race Conditions & State Integrity (playback_service.dart)

   • Resolved race conditions triggered by rapid track skipping by validating generation tokens across asynchronous boundaries.
   • Prevented outdated network requests and stale native operations from overriding active playback state or triggering false-positive error alerts.

4. DASH Assembly Memory Optimization (dash_assembler.dart)

   • Reduced concurrent download parallelism from 12 to 6 to avoid excessive heap allocations on high-bitrate tracks.
   • Cleared memory buffers immediately after chunks are written to disk, preventing large RAM spikes and GC-induced audio stutters.

5. UI Thread Responsiveness (signature_decipher.dart)

   • Offloaded player script regex parsing and cipher extraction to a background Dart worker isolate (Isolate.run), eliminating UI frame drops during YouTube stream resolution.

Testing & Verification

• Verified all 5 modified files pass static analysis with 0 lint/analyzer errors.
• Confirmed bit-perfect and shared-mode audio transitions function without driver crashes.
• Tested rapid track skipping in the queue to confirm no audio overlapping or stuck buffering indicators.