Record request validation review finding

docs/roadmap/remediation.md

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+# Request Validation Review Findings
+
+Reviewed commits `f315620`, `f3148bf`, and `60784e7` against the finalized
+[feature roadmap](validate.md) and [implementation plan](implementation.md).
+
+## 1. Reuse The Existing Preparation-Parity Test Helper
+
+Priority: P3 (test maintainability). Status: open.
+
+In [validate_request_contract_test.go](../../validate_request_contract_test.go),
+`TestValidateRequestMatchesPrepareContract` defines a local `testParity` closure
+at lines 25–45 that duplicates the package-level
+`assertValidateRequestParity` helper at lines 87–108. Both invoke `Prepare` and
+`ValidateRequest` and assert the same success/result and public-error behavior;
+the package-level helper additionally returns the successful prepared value.
+The nil-engine subtest repeats the same failure assertions again.
+
+Retaining separate copies makes future parity-assertion improvements require
+multiple edits and increases the risk that related tests diverge unnecessarily.
+This is a small cleanup, not a demonstrated functional or release-blocking bug.
+
+### Requested Remediation
+
+- Replace calls to the local closure with `assertValidateRequestParity` and
+  remove the redundant closure.
+- Reuse that helper for the nil-engine subtest as well; retain its
+  `ErrInvalidConfig` expectation.
+- Preserve all existing cases, public-error assertions, and no-model-call
+  checks. No production or public-contract changes are needed.
+
+Verify with `go test -race . -run '^TestValidateRequest'` and
+`git diff --check`, formatting the changed Go file.
+
+## Review Outcome
+
+The public method and shared facade helper match the intended architecture.
+No implementation gaps or unintended strengthening of contracts were found.
+The uncached full race-enabled suite, vet, maintained consumer examples, and
+implementation diff whitespace checks passed during review.