feat(derive): Haskell same-file REFS — intent-faithful single-target scope-walk .dl pack (retire native LocalRefs) — W23

[Disentinel]

Intent

Migrate Haskell same-file REFERENCE resolution (READS_FROM) off the native HaskellLocalRefs.hs resolver onto an in-engine @stdlib/haskell_local_refs* Datalog pack, faithful to the legacy resolver's intent — exactly ONE target per source (the legacy Map.fromList last-write-wins cardinality) — while fixing the cross-scope-collapse misroute the flat Map produced.

The native resolver was a flat (file, name) Map.fromList (last-write-wins). A naive multi-type union of that Map blew the edge count up ~×4.8 (spurious cross-namespace + foreign-scope-PARAMETER fan-out). This pack reproduces the legacy RETARGET-not-ADD cardinality via a nearest-binder scope-walk plus a single-target flat fallback.

Rides on the stack

• feat(haskell-analyzer): DoScope per do-block — do-bind binders in own scope (REFS single-target residual) — W23 #434 (DoScope) — single-target same-file resolution incl. per-do-block do-binds in their own scope. Gives the scope-walk its precise binder scoping (the REFS single-target residual was closed by DoScope).
• feat(haskell-globals): resolve prelude REFERENCEs to HASKELL_GLOBAL (FilterReferences pass) — W23 #435 (haskell-globals FilterReferences) — the prelude reference arm is re-homed out of the native LocalRefs into the haskell-globals runtime-globals pass. This fixes the old lost_vs_intent = 423 (prelude refs that the legacy resolver mapped but a pure same-file pack would drop). With the prelude arm dropped here and served by haskell-globals, those 423 are preserved.

What this pack does

Q1 applied. haskell_local_refs_nodes MINTS the virtual HASKELL_GLOBAL::<name> EXTERNAL_FUNCTION prelude endpoints; haskell_local_refs joins them as committed EDB (the js_runtime_globals two-pack nodes→edges split — a @materialize edge endpoint must be a committed node-ID column).

Resolution order in haskell_local_refs:

1. Nearest-binder scope-walk — a same-scope PARAMETER/VARIABLE local hit (the analyzer CONTAINS-parents these at the ref's own scope id — the dominant legacy bug) wins.
2. Single-target flat fallback over the value decl types via a namespace-PRIORITY ladder: FUNCTION > VARIABLE > CONSTANT > CONSTRUCTOR > RECORD_FIELD, then the TYPE namespace LAST (DATA_TYPE > TYPE_SYNONYM). A (file,name) with binders in several namespaces emits ONE edge to the highest-priority namespace (RETARGET, not ADD). Local FUNCTIONs are MODULE-flattened by the analyzer, so flat is the only recoverable resolution for them — no-worse than legacy.
   • PARAMETER is excluded from the flat arm: a flat PARAMETER target routes a ref to a FOREIGN scope's parameter — exactly the misroute bug re-introduced as fan-out. The only sound PARAMETER hit is the same-scope local arm.
3. Prelude arm DROPPED — the prelude global fall-through is no longer minted/resolved here; it is served by feat(haskell-globals): resolve prelude REFERENCEs to HASKELL_GLOBAL (FilterReferences pass) — W23 #435 haskell-globals (re-homed). The flat hit still suppresses what would have been the prelude fall-through, so mutual exclusion holds.

Differential vs intent

• false_added = 0 — a value binder always wins when present, so no spurious type/foreign edge is added.
• lost_vs_intent = 0 — the TYPE namespace is kept at LOWEST priority (not dropped), so a value REFERENCE whose only binder is a DATA_TYPE/TYPE_SYNONYM still resolves; the prelude 423 are preserved by haskell-globals.
• single-target: max_edges_per_source = 1 — pinned by the unit test (a ref to a 5-binder name + a foreign-scope PARAMETER emits ONE flat edge, to the FUNCTION).

Retirement (scoped)

• HaskellLocalRefs.hs removed; dropped from haskell-resolve.cabal other-modules.
• Orchestrator no longer dispatches the haskell-local-refs command (both resolve sites); same-file READS_FROM now runs in-engine. The KEPT arms (haskell-imports / haskell-cross-module-calls / haskell-globals) are cross-file / stdlib and the packs do NOT replace them.
• The haskell_local_calls pack is already on this base (feat(derive): Haskell same-file CALLS → intent-faithful single-target .dl pack (retire native LocalCalls) — W23 #428) — NOT re-introduced here; only the REFS pack + its registration.

Tests

• haskell_local_refs_scope_walk_fixes_cross_scope_collapse — nearest-binder scope-walk.
• haskell_local_refs_flat_fallback_is_single_target — the ×4.8 fan-out guard: single-target ladder, NO flat PARAMETER, TYPE-namespace lowest-priority still resolves (lost_real≈0).
• haskell_local_refs_prelude_fall_through — nodes-pack minting + EDB join + exclusive (provenance-scoped) mint.
• stdlib_pack_registry_resolves_names_in_canonical_order — registration/ordering with the new refs packs.

All green (cargo test --release --lib stdlib::tests: 57 passed; the 3 refs tests + the pre-existing calls test pass under haskell_local). rfdb-server + orchestrator build clean in release.

See _ai/research/haskell-resolve-intent-spec.md for the full intent spec.

Stacking

STACKED on #434 + #435 — merge those first. This branch's base (w23/haskell-refs-integration) already includes #434 (DoScope) and #435 (haskell-globals), so this branch contains them transitively.

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DO NOT MERGE — Vadim reviews; stacked on #434+#435.