Element Call: Call Awareness - Timeline Rendering

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Public facing issue. Work may be tracked on internal systems
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#### What would you like to do?

There is a disconnect in how clients represent a call took place in the timeline. EX shows "X started the call" and EleWeb only shares hidden events. We seek to align the platforms and instil confidence with users by sharing basic information about an Element Call event in-app.
It's important that:
* the room is an accurate representation of events that took place
* the information matches cross-platform
* we do not compromise too much information (GDPR rules, etc.)

#### Why would you like to do it?

- The timeline is not an accurate representation of the events in a room as Calls are not listed for users to view.
- We want to provide a clear and accurate representation of calls and join/leave notices with dates/times (no duration is needed at this stage).
- This should be available and **familiar** on all platforms.
- There are a few events that are sent to the timeline, we would need to filter irrelevant events and ‘listen’ to only the important ones.
- We do not want to fill the timeline with irrelevant information therefore there should be some sort of expand/collapse or consolidation mechanism.

Element X vs Desktop today:

#### How would you like to achieve it?
Design pending
**Inspiration**

### Milestones
- [ ] MVP: Basic text based representation in the timeline (incl. show/hide events for readability)
- [ ] Nice to have: "pretty" representation in the UI (maybe as a timeline widget or right panel information) TBD needs design workshop

No files, tests, or entry points are named. Start by resolving the pending design and locating the timeline implementations for the affected clients. Done means an agreed MVP represents call and join/leave events consistently, filters irrelevant events, and supports the planned readability mechanism.

Written by the indexing model from the issue text.