Reworks the clusterer's tick to handle multi-identity components and
re-evaluate prior merges. Two passes per tick:
Pass 1 — per-component reconciliation:
* Fresh component → mint identity (commit 4 path).
* Single-identity component → link unassigned observations.
* Multi-identity component → soft-merge: pick the smallest-uuid
winner deterministically, set merged_into_uuid on each loser,
link unassigned observations to the winner. Observations stay
FK'd to their original identity row — the merge is a soft
pointer, not a re-point. Audit trail preserved; cached
subscribers resolve through the chain.
Pass 2 — revocable-merge undo:
* For each merged-out identity, check whether its observations
still cluster with its winner's. If not, the merge is
contradicted by new evidence — clear merged_into_uuid and emit
identities_unmerged. The resurrected identity keeps its original
uuid, so subscribers that cached it during the merged interval
re-attach without a new lookup.
A pre-built merge-chain dict feeds Pass 1 so the effective-identity
lookup is O(1) per observation. The chain has a hop cap (paranoia
against accidental cycles in the underlying state).
Repo additions on BaseRepository + SQLModelRepository:
* list_all_identities() — includes merged-out rows.
* update_identity_merged_into(uuid, winner_or_None) — single
setter for both merge and unmerge.
DummyRepo coverage stub updated.
Tests:
* Two distinct identities bridged by a new observation merge with
the smaller uuid as winner.
* A pre-seeded soft-merge whose underlying observations diverge
gets revoked; resurrected uuid emerges with merged_into_uuid
cleared.
* Tick is idempotent under no state changes.
anti
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