Function drain_deferred_hidden_since_open 

pub fn drain_deferred_hidden_since_open(
    state: &mut State,
    now_ms: u64,
) -> Vec<Event>

Sweep hidden_since_open_deferred mirrors and emit drift for any that have crossed the placement grace boundary while still hidden and never foregrounded. Called from reducer::update AFTER every command processes so any recovery event the command itself dispatched (visible=true / foreground change / window closed) has a chance to clear the deferred state first. Without the AFTER ordering, a slow placement whose first post-grace event is the recovery itself would fire a spurious drift before the recovery runs (codex P2 PR #725 round 2).

Even with the AFTER ordering, this pass is the heartbeat that catches stuck-hidden windows whose own ReportHwndVisibilityChanged was suppressed during grace: any subsequent unrelated command past the grace promotes the deferred state to a fired drift.

(codex P2 PR #725 round 1 — addresses the “no recheck after grace” concern. Stuck-hidden windows that produce ZERO further commands are still a hole — we’d need a periodic timer for that — but realistic launcher traffic generates events constantly, so this catches the practical cases.)