fix(sasayaki): add media notification actions

[veritablevein]

Summary

• add concrete media notification actions for previous/play-pause/next
• keep the compact media style indices aligned with the actions actually added to the notification
• route notification actions to the existing Sasayaki playback callbacks

This is a smaller replacement for #72 that removes the settings toggle and device-specific fallback now that the SystemUI crash was traced to the incomplete media notification actions.

Testing

• ./gradlew test
• ./gradlew assembleDebug
• ./gradlew lint
• Tested on Hisense A5 Pro / Android 10: media notification no longer triggers the lock-screen sleep, and previous/play-pause/next controls work.

[HuangAntimony]

@codex review

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Add required Sasayaki release docs

This adds user-visible Sasayaki notification controls, but the commit leaves docs/CHANGELOG.md's [Unreleased] section empty and does not update docs/TODO.md. The repo instructions in AGENTS.md require user-visible fixes/features to be recorded in the changelog and TODO to be updated in the same commit, so this release would otherwise omit the fix from user-facing notes and current project status.

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