test+docs: add tests for QualityDirective, ParticipantQuality; update docs

- QualityDirective signal roundtrip tests (with/without reason)
- ParticipantQuality unit tests (initial tier, degradation, weakest-link)
- Updated PROGRESS.md with desktop adaptive quality, relay coordinated
  switching, Oboe state polling entries
- Updated ARCHITECTURE.md SFU fan-out rules with QualityDirective
- Updated PRD-coordinated-codec.md with implementation status
- 312 tests passing across all modified crates

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

scripts/build.sh

@@ -22,6 +22,7 @@ set -euo pipefail
 #   ./scripts/build.sh --init                First-time setup (clone + Docker image)
 #   ./scripts/build.sh --install             Download APK + adb install locally
 #   ./scripts/build.sh --release             Release APK (not debug)
+#   ./scripts/build.sh --android64          Release arm64 APK (shorthand for --android --release)
 # =============================================================================
 
 NTFY_TOPIC="https://ntfy.sh/wzp"
@@ -48,6 +49,7 @@ while [ $# -gt 0 ]; do
         --install)  DO_INSTALL=1 ;;
         --init)     DO_INIT=1 ;;
         --android)  BUILD_ANDROID=1; BUILD_LINUX=0 ;;
+        --android64) BUILD_ANDROID=1; BUILD_LINUX=0; BUILD_RELEASE=1; BRANCH="main" ;;
         --linux)    BUILD_ANDROID=0; BUILD_LINUX=1 ;;
         --all)      BUILD_ANDROID=1; BUILD_LINUX=1 ;;
         --release)  BUILD_RELEASE=1 ;;