…ers and refine UI transitions

- **Gesture Handling**:
    - Add `onDragCancel` to `SheetVerticalDragGestureHandler` to ensure consistent state cleanup.
    - Track `isSheetDragGestureActive` across player components to coordinate placeholder transitions with user interaction.

- **Placeholder Logic**:
    - Introduce `switchOnDragRelease` preference to defer content/placeholder swapping until a drag gesture is finished, bypassing percentage-based thresholds.
    - Update `DelayedContent` to handle the new drag-release logic, ensuring placeholders only transition when the sheet is stable.

- **Settings & Preferences**:
    - Add "Switch on drag release" toggle to Experimental Settings.
    - Enable `usePlayerSheetV2` by default.
    - Update `UserPreferencesRepository` and `SettingsViewModel` to persist and manage the new preference.

- **UI Refinements**:
    - Adjust corner radius interpolation in `SheetVisualState` to transition to `0.dp` when fully expanded for a more immersive look.
    - Disable threshold sliders in settings when "Switch on drag release" is active to prevent conflicting configurations.