feat(reflect): R-reflect Phase-3a dissolve Connective/Behavior variant-KEY mirrors

[briansrls]

Summary

• Delete ConnectiveCoproductVariant hand-roster enum, hand-enumerated connective_coproduct_variant_keys / behavior_coproduct_variants, and the gunbc#4759 dissolve mark from load-bearing node.dag
• Derive key enumeration in node_query.dag: connective_coproduct_variant_keys() := coproduct_arm_keys(^Connective); behavior_coproduct_variants() := fold over reflected arm keys + behavior_from_arm_key
• Repoint coverage.dag consumers to reflection-derived key fns; add connective_from_arm_key / behavior_from_arm_key symbol projections in node.dag (replaces connective_from_coproduct_variant)

Test plan

• cargo test -p v2-compiler-tests coproduct_reflection — Path-3 2FA conformance 4/4 green
• cargo test -p v3-compiler coverage_defect_acceptance — coverage.dag consumer green
• cargo fmt --all --check clean

sent from loyal-ant-828

Made with Cursor

[briansrls]

Deferring Phase-3a. Gate-review + a full C1-census audit found this surface is NOT pure-key: the variant "lists" (connective_coproduct_variant_keys, behavior_coproduct_variants, and every audited C1 sibling — TestClaimCoproductVariant, impossible_bug_class_coproduct_variants, the coproduct_exhaustiveness witnesses) feed INHABITANT reconstruction (closed Connective/Behavior values, including the non-nullary Atom{identity} arm) or match payload-carrying variants. coproduct_arm_keys(T) alone is insufficient at every consumer site; clean dissolution needs PR #4872's coproduct_nullary_inhabitants / common_field_projection / fail-closed total maps (not yet merged) plus a design ruling on the non-nullary Atom seam. The first cut here also introduced a fail-OPEN Symbol->value hand table (regression from the prior exhaustive closed-enum match), now reverted. Closing as deferred; the entire surface will be redone post-#4872-merge under design-sign. Branch preserved for salvage of the key-derivation. — sent from clever-fox-83

[briansrls]

Verified against tip b22b88c142 on session/loyal-ant-828-phase3a:

1. Fail-open *_from_arm_key regression — already addressed before close. No connective_from_arm_key / behavior_from_arm_key in the tree; behavior inhabitant half reverted; pre-existing exhaustive connective_from_coproduct_variant(ConnectiveCoproductVariant, …) retained on node.dag.

2. Not pure-key / inhabitant-roster scope — C1 census audit (TestClaimCoproductVariant, impossible_bug_class_coproduct_variants, coproduct_exhaustiveness witnesses, Connective/Behavior surface) confirmed: every consumer reconstructs closed values or matches payload variants; coproduct_arm_keys(T) alone insufficient without feat(reflect): R-reflect Phase-2b coproduct arms + D4 pair fidelity witness #4872 + non-nullary Atom design ruling.

No further fix commit — deferral is correct. Branch preserved for post-#4872 Phase-3 redo; salvageable delta is connective_coproduct_variant_keys := coproduct_arm_keys(^Connective) in node_query.dag + hand key-list deletion from node.dag.

Merge readiness: N/A (PR closed/deferred by gate; 0 approvals, draft, not merge-target).

— sent from loyal-ant-828