feat: add setting to ignore silent notifications

[anuragdeshpande]

Summary

Modern Android versions allow notifications and notification channels to be marked as Silent or Default (Alerting). Silent notifications appear in the "Silent" section of the notification shade without playing sound, vibrating, or showing heads-up banners.

Previously, Expressive Cutout surfaced cutout bubble animations for all clearable notifications regardless of whether they were marked as silent or alerting. This PR introduces an opt-in toggle under Settings > Behavior ("Ignore silent notifications") that respects this Android system configuration and suppresses cutout bubbles for silent notifications.

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What was done & Why

1. Notification Silence Detection (NotificationClassifier & CutoutNotificationListenerService)

   • Implemented NotificationClassifier.isSilent(...) to evaluate notification importance and ambient status (importance < IMPORTANCE_DEFAULT or isAmbient == true), with backward-compatible priority fallback.
   • Updated CutoutNotificationListenerService.onNotificationPosted to receive RankingMap from Android's NotificationListenerService and tag CutoutSignal.Notification with isSilent: Boolean.

2. User Preference & DataStore (BehaviourSettings, BehaviourPreferences, AppViewModel)

   • Added ignoreSilentNotifications: Boolean = false to BehaviourSettings.
   • Added DataStore persistence, JSON serialization/deserialization for settings backup/restore, and ViewModel binding.

3. Overlay Bubble Filtering (IslandOverlayController)

   • When ignoreSilentNotifications is enabled, IslandOverlayController skips displaying cutout bubble overlays for notifications where signal.isSilent == true.

4. Settings UI (BehaviourScreen, strings.xml)

   • Added the "Ignore silent notifications" toggle card under Settings > Behavior.

5. Testability & Unit Tests (SilentNotificationTest)

   • Introduced JUnit test support to the project (testImplementation(libs.junit) in build.gradle.kts and libs.versions.toml).
   • Added SilentNotificationTest covering importance classification, ambient status, fallback priorities, signal flags, and filtering logic to guarantee regression prevention.

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How it helps the Application & System

• User Experience: Users who intentionally silence low-priority notifications (e.g. background syncs, weather updates, ongoing status updates) won't have their screen interrupted by popping cutout bubbles.
• System Resource Efficiency: By dropping silent notifications early when configured, the overlay avoids unnecessary compose layout passes and spatial spring animation overhead.
• Improved Codebase Quality & Testability: Adds unit testing infrastructure and isolated unit tests to ensure future notification parsing and filtering remains reliable.

[EvanKoe]

Same as #33 : I need you to rebase from dev, especially on the CutoutNotificationListener, who got a big refactor in #27

[anuragdeshpande]

Rebased onto dev and resolved conflicts with the recent listener refactor. Ready for review!

[EvanKoe]

Lgtm, tested on my end.