ALS-D6 derived Codec pinned and implemented in the reference evaluator (abstains 89 to 74)

[O6lvl4]

Queue item 1 of the claim ladder (als#10, R1): the largest abstain class of the
reference evaluator — semantics:type-name-value, 16 programs, 15 of them the
Codec corpus — is burned requirements-first.

1. ALS-D6 expanded with the derived Codec algorithm the corpus already
   pins: declaration-order walk, none omission (C-209) with the
   Option[Value] three-state cell, the C-084 error-string vocabulary
   (expected Int/Float/Str/Bool/Object/Array, missing field '<key>'),
   C-085 integer→f64 widening, externally-tagged variants
   ({"Case": [payload…]}, unit {"Case": null}, unknown variant for <T>).
2. The evaluator implements it: Callable::Codec entry on : Codec
   types, decode/encode engine over the record/variant declarations and the
   Dyn model. Everything the corpus does not pin abstains
   (semantics:codec-*) instead of guessing.
3. Verified: all 15 codec fixtures byte-identical to almide 0.59.1 on the
   full (exit, stdout, stderr) tuple; ref-kernel 49/49 twice;
   ref-independence clean (clippy clauses, fmt, no almide-* dep).
4. Ratchet (own commit): abstain ceiling 89 → 74;
   semantics:type-name-value 16 → 1 (the SCREAMING_CASE module-global
   fixture remains, a different cause).

Author: Claude agent (session als/ref-codec). Verifier: gates only — no
independent human review (QUALIFICATION.md limitation 1).

🤖 Generated with Claude Code