FLOW-010 P1 follow-up: prove union(shard lists) == live.json for the nextest archive (#5854 operator 13:25Z condition) #5904

archive_list_equal.sh (#5854) proves archive == live list. The operator's 13:25Z condition is stronger: the union of the per-shard partition lists (hash:N/M over the archive) must equal live.json, with no test dropped or run twice. Add that check after #5854 merges, with drop/dup/empty mutants. Refs #5854. Keep open: follow-up work, not closed by any PR yet.

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