changelog: update fixed issues list, remove known issues

changelog.txt

@@ -7,8 +7,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
 ## [Unreleased]
 
 ### Fixed
-- Device restore path passes invalid device name "system default" to SDL (should pass "" for default)
-- Active device highlight incorrect when using default device
 
 ### Changed (Major Refactors)
 - Mixer package: extract wpctl calls behind an interface
@@ -19,6 +17,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
 - Play() deadlocks when called before device is open (recursive SwitchDevice -> Play)
 - Audio volume silently zeroed after switching output devices (Init used hardcoded 0.20; SwitchDevice did not restore saved volume)
 - SwitchDevice not persisted to database across restarts (caller now saves to AppConfig)
+- Device restore path passes invalid device name "system default" to SDL (now passes "" for default)
 - Stop() no-op when audio toggled off mid-playback (removed AudioEnabled guard from Stop)
 - App shows "READY" before audio files finish downloading (state machine now gates READY on download completion via DOWNLOADING_ASSETS state)
 - Download failure no longer silently allows READY (downloadFailed flag prevents premature READY)
@@ -26,8 +25,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
 - F2/F3 keybinds now work during DOWNLOADING_ASSETS (blocked only during early prerequisites: no wifi, no email, no license key)
 - Active device highlight incorrect when using default device (default device now maps to first SDL device)
 
-### Known Issues
-
 ### Added
 - Human-readable audio device names (Built-in Speakers, HDMI/TV/Monitor)
 - Unit tests for mixer package (parseSinks, parseSinkLine, ConvertVolume)