CORE-2: Map primitive + Element_id (UUID v5) + Value

[vieiralucas]

Summary

• Adds Element_id (UUID v5 derived from (parent_id, key)), Value (closed sum: Scalar | Element), and Map (LWW per slot with Live/Tomb tombstones).
• Wire-level Map ops trimmed to Set + Delete only. initOnce/replace were SDK guardrails that became dead surface once deterministic Element_id removed the concurrent-init orphan footgun.
• apply returns (t', released_ids) — both displaced Live Element refs and stranded losers from losing Set ops with unique Element values. Doc layer decides orphan status by cross-checking reachability.
• ARCHITECTURE.md updated: Map section rewritten around deterministic id, Map Slot Safety reframed, op kind enum trimmed.
• Closes KANBAN CORE-2.

Modules

Module	Surface	Notes
Element_id	root, derive ~parent ~key, to_string/of_string, to_bytes/of_bytes, compare, equal, pp	UUID v5 via Uuidm.v5. Root = Uuidm.nil. Two clients computing same (parent, key) arrive at same id without coordination.
Value	scalar = String | Int int64 | Float | Bool | Null; t = Scalar of scalar | Element of Element_id.t; pp/equal	Blob constructor lands with the blob subsystem.
Map	empty ~element_id, element_id, apply ~op ~op_id ~lamport -> t * released, get/keys/entries/cardinal, equal/pp	LWW with (lamport, op_id) tiebreak. Tombstones survive Delete so stale Sets cannot resurrect deleted keys.

Released-ref semantics

Across both win and lose branches of apply:

• Winner displaces Live Element with different id -> displaced id is released.
• Winner displaces Live Element with same id (deterministic-SDK concurrent case) -> not released; id is still in slot via winner.
• Loser is a Set with unique Element id -> stranded id is released.
• Loser is a Set with same Element id as winner / a Scalar / a Delete -> nothing released.

Commits

• d232125 CORE-2: Map primitive + Element_id (UUID v5) + Value
• 2965b4d style: ocamlformat sweep (margin 90, break-infix fit-or-vertical)

Test plan

• `dune build` clean
• `dune runtest --force` -- 124 tests pass across 10 suites
  • element_id: 17 (root round-trips, derive determinism on (parent, key), nested chain, v5 version-nibble check, malformed/wrong-length rejects, 4 qcheck properties)
  • value: 11 (scalar variant equal+pp, t equal+pp, distinguishes Scalar vs Element)
  • map: 22 (empty, set LWW lamport+op_id tiebreak, delete LWW + survives stale Set, released_refs split into displaced/stranded/same-id/scalar cases, idempotency, concurrent deterministic convergence, keys/entries/cardinal sort, equal/pp)

---

Summary by cubic

Implements CORE-2 by adding a Map CRDT with deterministic Element_id (UUID v5 from (parent_id, key)) and reducing wire ops to map.set/map.delete so concurrent slot init converges without orphans. Also updates tests for qcheck-core API changes to keep CI passing.

• New Features

  • Element_id: UUID v5 from (parent_id, key); root is nil. Same (parent, key) → same id across clients.
  • Value: Scalar (String, Int int64, Float, Bool, Null) or Element of Element_id.
  • Map: LWW per key with lamport/op_id tiebreak; deletes leave tombstones. apply ~op ~op_id ~lamport returns (t', released_ids) for displaced or stranded Element refs. SDK get-or-create helpers (e.g. Map.text key) derive the id and emit Set, so concurrent init converges.
  • Docs: Map section rewritten around deterministic ids; op kind enum trimmed to map.set and map.delete.

• Migration

  • Emit only map.set and map.delete on the wire; initOnce/replace move to SDK sugar.
  • Handle released_ids from Map.apply in the doc layer to decide orphaning via reachability.

^{Written for commit 2f01725. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

No issues found across 38 files

_{Re-trigger cubic}