Player API: PlayerTarget & Features

[mihar-22]

Update core/dom features to use PlayerTarget pattern with availability states.

Ref #320

Scope

Component	Description
PlayerTarget type	{ media: Media, container: MediaContainer | null }
FeatureAvailability	'available' | 'unavailable' | 'unsupported'
Update features	All features use PlayerTarget instead of HTMLMediaElement
Volume availability	Add volumeAvailability state with iOS Safari check
Feature bundles	video and audio feature arrays
Pre-built selectors	selectPlayback, selectVolume, selectTime, selectSource, selectBuffer

Key Types

interface PlayerTarget {
  media: Media;
  container: MediaContainer | null;
}

type FeatureAvailability = 'available' | 'unavailable' | 'unsupported';

Files

• packages/core/src/dom/types.ts (new)
• packages/core/src/dom/store/features/playback.ts
• packages/core/src/dom/store/features/volume.ts
• packages/core/src/dom/store/features/time.ts
• packages/core/src/dom/store/features/source.ts
• packages/core/src/dom/store/features/buffer.ts
• packages/core/src/dom/store/features/bundles.ts (new)
• packages/core/src/dom/store/selectors.ts (new)
• Tests for all above

Acceptance Criteria

• PlayerTarget and FeatureAvailability types exported from @videojs/core/dom
• All features updated to use target.media instead of target
• Volume feature exposes volumeAvailability state
• features.video and features.audio bundles exported
• Pre-built selectors exported: selectPlayback, selectVolume, etc.
• All tests pass

SP: 2