Audio in+out support

[SaicharanKandukuri]

What changed

• add an app-owned PulseAudio 17/OpenSL ES runtime for Linux playback and optional microphone input
• expose per-system speaker and microphone controls, with Android permission and privacy handling
• connect supervised terminal, desktop, and Linux app sessions over authenticated device-local loopback
• package checksum-pinned runtimes for all supported ABIs with a reproducible build script
• document the audio architecture and add unit and device probes

Why

Linux applications previously had no supported path to Android audio devices. This gives PRoot sessions a managed PulseAudio endpoint without requiring an audio daemon inside every rootfs.

Impact

Speaker output is enabled by default. Microphone input remains opt-in per Linux system and requires Android runtime permission. Direct ALSA-only clients still need a PulseAudio compatibility plugin.

Root cause addressed

PRoot could see a bind-mounted Unix socket but could not reliably connect through it. The bridge therefore binds PulseAudio only to 127.0.0.1 and authenticates guests with a private bind-mounted cookie.

Verification

• ./gradlew testDebugUnitTest assembleDebug lintDebug
• update-key signed assembleRelease
• installed over v0.0.9 on a Pixel 6 without clearing app data
• pactl info connected from Ubuntu/XFCE and reported the uDroid sink
• pavucontrol displayed OpenSL ES Output
• paplay /usr/share/sounds/freedesktop/stereo/complete.oga completed successfully
• git diff --check