Renew presence from the socket's current state; scope open dialogs to their page

From Greptile on #243:

- A renewal awaits its pass check, then saved the socket's state from
  before the wait: a clear (or cursor move) that arrived meanwhile was
  undone, and newcomers saw a stale "editing". It now renews what the
  socket holds after the wait, and nothing for a socket that closed.
- A lineup dialog edits the groups of the page it opened on. Left open
  across a page change, it no longer counts as editing whatever shares
  its item ids on the new page.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
63a431f533Dara Adedeji committed on 10/3/2026, 5:29:38 PMparent16d3bac

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