Load the latest event from each event file in the events directory.
Returns a map of pane_id → LatestEvent, keeping only the highest-timestamp
entry per pane_id. This deduplicates across multiple files that share a
recycled pane ID, ensuring the current session’s events always win.
Remove event files whose last event matches the given pane_id.
Called when a new window is created to prevent stale events (from a previous
session that used the same recycled tmux pane_id) from contaminating state.