Remote Volume Controller v0.2.1

Stage 2 correction build.

Fixes:

• Windows phone-volume slider now moves locally while dragging and sends one command after release, then applies the confirmed Android value.
• Windows no longer opens a new QUIC connection to the phone every two seconds. A remote state check runs once per minute only while the window is visible, and immediately when the window regains focus.
• Android exits its receive loop when the endpoint closes instead of spinning.
• Repeated Android receive failures now use bounded exponential backoff up to 64 seconds.

Acceptance status: existing Stage 2 scenarios passed on the owner's Poco F5. Stage 2 remains IN PROGRESS pending confirmation that v0.2.1 fixes slider smoothness and excessive background battery/network usage.

Artifacts:

• RemoteVolumeController-Windows-v0.2.1-debug.exe — unsigned debug/test build
  SHA-256: d109e4d6929b3de8dbb96a4bb5d6100076bf402e1a64fcda79152d4d18a593cc
• RemoteVolumeController-Android-v0.2.1-debug.apk — debug-signed arm64-v8a APK
  SHA-256: a3d4630f5129848c8768dfd02ff3d25c7e719a69e30a98945ded3019cb092d6e