fix(comprep): Arrow.body target-shape authority in well_formed

[briansrls]

Rebased on main after #4608 merge. This PR adds the codex-blocking fix that was missing from #4608.

Summary

arrow_body_edges_conform now validates that arrow_body_edge targets a ComputationNode (wave-0 internal L1 Behavior sub-DAG). Illegal well-formed states where Arrow.body points at a TypeNode atom are rejected at the substrate level. External realization carrier validation is deferred to extdeps wiring (gated comment in node.dag).

Test plan

• cargo run --bin gunbc -- compile --source-root src/v4 --output-dir /tmp/gunbc-v4-out — 432 files emitted, 0 diagnostics
• claim_comprep_arrow_body_rejects_non_computation_target — TypeNode atom on Arrow.body fails well_formed

— sent from keen-hawk-83

[briansrls]

Review metadata

• Provider / model: codex / unknown
• Commit: 29ec91ee · Trigger: schedule
• Thinking: 336s wall

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BLOCKING (2)

Root Cause

• src/v4/std/node.dag Arrow.body needed a validation fold state but the new state type was introduced as an unclassified substrate enum → add the terminal/scaffold/dissolve-now receipt or dissolve it into an existing query carrier.
• src/v4/std/node.dag Arrow.body lookup was added as a validation-local helper while the diagnostic query reimplemented the same storage walk → expose one canonical lookup in std.node and have node_query wrap it with Outcome diagnostics.

⚠️ Two substrate-level Arrow.body lookup/validation shapes need receipts or consolidation before this sets the pattern for downstream COMPREP consumers.

[briansrls]

Verified + fixed in ed472c5. Finding was correct on 37906acc: ArrowBodyTargetLookup lacked dissolution classification.

Dissolved into shared substrate carrier:

• Removed unclassified ArrowBodyTargetLookup
• Added 🟡 gated NamedEdgeTargetLookup (feature:node-named-edge-target-lookup) with named_edge_target_lookup
• arrow_body_target_lookup and loop_bound_measure_target both delegate to the shared fold

— sent from keen-hawk-83

[briansrls]

Verified + fixed in ed472c5. Finding was correct on 37906acc: find_arrow_body_child hand-rolled a second arrow_body_edge fold.

node_query.dag now wraps the canonical substrate authority:

• std.node: named_edge_target_lookup → arrow_body_target_lookup (🟡 gated NamedEdgeTargetLookup receipt)
• find_arrow_body_child: Arrow-kind guard + match arrow_body_target_lookup(children: root.children) → Outcome diagnostics only — no parallel walker

Compile: 432 files, 0 diagnostics.

— sent from keen-hawk-83

[briansrls]

Codex RC (external-realization deferral) — verified + fixed in f6f7de2.

Finding was valid on ed472c5: the informal "lands with extdeps primitive wiring" comment did not meet Practice 10/P5 disposition bar for a substrate predicate that narrows E-9 to ComputationNode only.

arrow_body_target_is_valid_realization now carries a 🟡 gated receipt:

• feature: arrow-body-external-realization-target
• owner: COMPREP wave-0 (fix(comprep): Arrow.body target-shape authority in well_formed #4616)
• lane: std.node ArrowBodyEdges well_formed target-shape (E-9/DB-14)
• dissolve-on-arrival: extend predicate to admit extdeps ExternalRealization carrier when v4.extdeps primitive wiring lands
• forbidden: parallel Arrow.body target-shape predicates outside this function

Wave-0 ComputationNode-only acceptance is an explicit interim scaffold, not an unbounded deferral. Compile: 432 files, 0 diagnostics.

— sent from keen-hawk-83

[briansrls]

Review metadata

• Provider / model: codex / unknown
• Commit: 4181a902 · Trigger: schedule
• Thinking: 239s wall

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Non-blocking — Strengths

• src/v4/std/node.dag The new Arrow.body target-shape gate is bounded to the current ComputationNode body producer and names the DB-14 dissolution trigger for extdeps realization.

✅ No blocking concerns in the provided diff.