Add auto-play consecutive voice messages in timeline

[kalix127]

Content

Add auto-play for consecutive voice messages in the timeline. When a voice message finishes playing, if the next chronological message is also a voice message, it automatically starts playing. The chain continues until a non-voice message is encountered or the end of the timeline is reached.

Key changes:

• New VoiceMessageAutoplayManager interface (voiceplayer API) and DefaultVoiceMessageAutoplayManager implementation (voiceplayer impl, RoomScope singleton)
• Manager observes MediaPlayer.state for isEnded transitions and triggers playback of the next consecutive voice message
• VoiceMessagePresenter listens for reset requests and cancels autoplay on manual pause
• TimelinePresenter feeds current timeline items to the autoplay manager on each update
• Virtual items (day separators, read markers) are skipped when checking adjacency

Motivation and context

Closes #4618

This is a standard feature in almost every modern messaging app.

Screenshots / GIFs

Tests

• 1. Send 2+ voice messages in a row in a test room
• 2. Play the first one, when it ends, the next should auto-start
• 3. Insert a text message between voice messages, autoplay should stop at the boundary
• 4. During autoplay, manually tap pause, chain should stop
• 5. During autoplay, tap a different voice message, chain should cancel and play the tapped one
• 6. Replay the first voice message after a completed chain, autoplay should work again
• 7. Scroll voice messages off-screen during autoplay, playback should continue unaffected

Tested devices

• Physical
• Emulator
• OS version(s): Android 15

Checklist

• Changes have been tested on an Android device or Android emulator with API 24
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/element-hq/element-x-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request title will be used in the release note, it clearly define what will change for the user
• Pull request includes screenshots or videos if containing UI changes
• You've made a self review of your PR

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Open questions

@jmartinesp

1. Transition sound: Currently there is no sound effect played between consecutive voice messages during autoplay. Open to suggestions on whether we should add one (e.g. a short tick/beep) and if so, what would fit best.
2. User setting: Autoplay is always enabled for now. Open to feedback on whether we should add an on/off toggle in user settings.

[github-actions]

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[bxdxnn]

LGTM, but the common behavior is to also play a sound between messages before playing them.

[kalix127]

LGTM, but the common behavior is to also play a sound between messages before playing them.

I know, in fact I asked for feedback and suggestions on which sound to use. Honestly, the options are endless.

[kalix127]

In the meantime, I've added code to play a sound when it moves on to the next audio recording. Right now, it uses the same default notification sound, but all you have to do is replace it with a different sound, and then it's all set.

@americanrefugee , do you have any suggestions for a sound to use?
I've tried changing the notification sound in a few different ways, but with little success.

[americanrefugee]

@americanrefugee , do you have any suggestions for a sound to use?

Actually I think @amshakal would be a better person to ask since she reviewed the notification sounds in general recently.