fix(sasayaki): publish complete system media controls

[veritablevein]

Fix the Sasayaki media notification so Android SystemUI receives a complete, self-consistent set of media actions instead of compact action indices without matching notification actions.

The Hisense A5 Pro / Android 10 lock-screen sleep was caused by the OEM SystemUI crashing while inflating the Sasayaki media notification. The previous workaround disabled the notification path in Auto mode on that device. This update keeps system media controls enabled in Auto and fixes the notification structure directly:

• add explicit Previous / Play-Pause / Next notification actions before using them in setShowActionsInCompactView
• route notification button taps back to the existing Sasayaki cue/playback callbacks, so Next Cue does not depend on platform skipToNext() playlist semantics
• keep the Auto / On / Off setting, with Off as a manual fallback if another device-specific SystemUI issue appears later
• update docs and tests to reflect that Auto now publishes usable system media controls

Verified:

• ./gradlew test
• ./gradlew assembleDebug
• ./gradlew lint
• Real Hisense A5 Pro Android 10: Auto shows media controls without lock-screen sleep; notification Previous, Play/Pause, and Next controls work; Off suppresses the media notification fallback.

[veritablevein]

Superseded by #75, which keeps the fix minimal and only changes the media notification actions needed to resolve the SystemUI crash.