Fewer tab and group moves per run, to reduce Chrome instability: windows that are already packed are skipped, groups are collapsed once at the end of a run, and identical queued requests are coalesced.
Fewer duplicate merges and window-wide tab queries per Group run.
Gentler retry when the browser rejects a group operation: a plain retry first, and ungrouping only as a last resort.
A hung browser API call can no longer block the action queue (each action is abandoned after 120 s).