Prepending older actions changes `actions`, and the bottom-pinning effect
watches `actions`. If nothing had un-pinned the view first, loading earlier
turns scrolled straight past them to the newest one -- the reader asks to go
back and the story throws them forward.
Scrolling up is what normally un-pins, so the case that breaks is the one
where the reader never scrolled: a window short enough to fit the viewport,
where the "N earlier moments" button is the only way back and the button is
what fails. Reading backwards is the opposite of following along, so a prepend
now clears the pin explicitly rather than relying on a scroll having happened.
Found by re-reading this path rather than by running it -- the scroll
behaviour is the one part of the paging work nothing exercises, since the
frontend has no test runner.
Also holds off three seconds after a failed page fetch. Parked near the top,
momentum scrolling calls this dozens of times a second, and against an
endpoint that is failing that is a retry storm rather than a retry.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Dvvqn9ZDR4ixeFPHNbww7
