root 7d6636b33e validator: align ValidationError JSON to Rust serde shape (6/6 parity)

Closes the 2026-05-02 parity finding: validator_parity probe found
5/6 body shapes diverging because Go emitted {"Kind":"...","Field":"...","Reason":"..."}
while Rust emits the externally-tagged-enum {"Schema":{"field":"...","reason":"..."}}.
A caller parsing the error envelope would break silently in cutover.

## Changes

internal/validator/types.go:
- Custom MarshalJSON emits the Rust shape:
    Schema:       {"Schema":      {"field":"x","reason":"y"}}
    Completeness: {"Completeness":{"reason":"y"}}
    Consistency:  {"Consistency": {"reason":"y"}}
    Policy:       {"Policy":      {"reason":"y"}}
- Custom UnmarshalJSON accepts BOTH the new Rust shape AND the legacy
  flat shape (migration safety for any persisted error rows).
- Unknown variants (e.g. a future Rust addition Go hasn't learned)
  surface as an Unmarshal error, not a silent default.

internal/validator/types_test.go:
- 4 pinning tests anchor the wire format. Failing them = wire-format
  drift; the parity probe is the secondary line of defense.

scripts/validatord_smoke.sh:
- Updated probes to read the new variant-name shape (jq keys[0],
  .Schema.field) instead of legacy .Kind/.Field.

## Verification

- internal/validator unit tests: PASS (4 new + all existing).
- cmd/validatord HTTP tests: PASS (UnmarshalJSON falls through to flat
  shape so existing tests reading ValidationError still work).
- validatord_smoke.sh: 5/5 PASS through gateway :3110.
- validator parity probe re-run: **6/6 match** (was 1/6).

## Pattern

Per architecture_comparison's "use the dual-implementation as a
measurement instrument" thesis: a parity probe surfaced this gap;
50 LOC of MarshalJSON closed it; 4 pinning tests prevent regression;
the probe is the longitudinal gate. Cutover-friendly direction (Go
matches Rust) chosen because Rust is the existing production
contract.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-05-02 04:49:28 -05:00

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Validator parity probe — Rust :3100 vs Go :4110

Date: 2026-05-02T09:47:49Z Rust gateway: http://127.0.0.1:3100 · Go gateway: http://127.0.0.1:4110

Identical POST /v1/validate request → both runtimes. Match = identical HTTP status + identical body (modulo elapsed_ms).

Case	Rust status	Go status	Status match	Body match
playbook_happy	200	200	✓	✓
playbook_missing_fingerprint	422	422	✓	✓
playbook_wrong_prefix	422	422	✓	✓
playbook_empty_endorsed	422	422	✓	✓
playbook_overfull	422	422	✓	✓
fill_phantom	422	422	✓	✓

Tally: 6 match · 0 diff (out of 6 cases)

728 B Raw Blame History

Validator parity probe — Rust :3100 vs Go :4110

728 B

Raw Blame History