[codex] skip request validator when disabled

[k-kinzal]

Summary

Fixes request handling so disabling request validation actually prevents the request validator from running.

Root Cause

Interceptor::resolveOperation() still called Validator::validateRequest() when request validation was disabled, then swallowed ValidationException. That meant invalid requests could still pay validation cost, and response validation could be skipped because no operation address was available.

Changes

• Resolve OperationInfo from the schema lookup before operation address resolution.
• Only call the request validator when request validation is enabled.
• Build an OperationAddress from the matched operation when request validation is disabled so response validation still works.
• Add a regression test for response validation with request validation disabled.

Validation

• composer test
• composer lint