Codex follow-up finding: _lastMessageUpwardIntentMs/_lastNonMessageScrollIntentMs
initialized to 0, so _recentMessageUpwardIntent() returned true for the first 2s
after load (performance.now() < MESSAGE_UPWARD_INTENT_MS=2000) even with no user
scroll — which would disable the new #3319 retry guard during initial load. Sentinel
-Infinity makes 'no event recorded yet' read as no-intent. Also tightens the
pre-existing scrollIfPinned/settle callers that read the same helpers.
5d4ce75041
