rooms often open uwith the wrong scroll offset

i was talking in HQ, then went away and did other things and the conversation progressed there. In reopening HQ the timeline was scrolled back much further than I was at when I left (and there was both a RM bar and a 'jump to 11 unread msgs' bar). It feels like it is trying to remember where i was when i was last in the room and getting it wrong. I would much prefer it just always opened the room at the most recent messages, as per web

Start by reproducing the issue in an iOS room after leaving while the conversation progresses, then inspect the room reopening and timeline scroll-restoration entry points. Compare the behavior with the web app. Done means reopening the room shows the most recent messages rather than an older saved offset, with the unread and room-member bars behaving consistently.

Written by the indexing model from the issue text.