Presence indicators always show offline in room list despite receiving m.presence events

## Environment
- Element Web version: 1.12.21
- Synapse version: 1.155.0
- Browser: Chrome 149 on macOS
- Server: Debian 13, Raspberry Pi 5

## Steps to reproduce
1. Log in as user A on Element Web
2. User B is online on Element X iOS with "Share presence" enabled
3. Users share a joined room
4. Observe user B presence indicator in user A room list

## Expected
Green "online" circle next to user B

## Actual
Always shows "Offline" (empty gray circle) for ALL other users

## Evidence
1. Direct presence API works: GET /presence/@userB/status returns {"presence":"online","currently_active":true}
2. Presence events ARE delivered via /sync: incremental sync with since=token correctly returns m.presence events for other users
3. User A own presence indicator works correctly in the same UI
4. Sign out + clear site data + fresh login does NOT fix it
5. The same accounts work correctly in Element Desktop and Element X iOS

The presence data arrives in /sync but the room list rendering does not update the indicator. Related to #32632.

Start by tracing how incremental /sync m.presence events reach the room list rendering, comparing other users' indicators with the working own-user indicator. Use the reproduction steps and the related #32632 issue as context. Done means the room list shows other users as online when the received presence data reports online.

Written by the indexing model from the issue text.