Add ENS TXT compatibility validation for signer proof checks

[GsCommand]

Motivation

• Ensure CLAS canonical proof verification can be constrained by ENS TXT records (cl.sig.* and cl.receipt.signer) without hardcoding production keys.
• Enforce fail-closed behavior by requiring metadata.proof.signature.kid for canonical proof verification.
• Provide a small compatibility surface so callers can compare resolved ENS values to receipt proofs when ENS verification is used.

Description

• Added EnsVerificationRecord type and optional ensRecord parameter to verifyCommandLayerReceipt to allow ENS-driven checks of kid, canonicalization, and signer identity.
• Require metadata.proof.signature.kid presence during verification and return explicit error reasons on mismatch.
• Exported EnsVerificationRecord from the package root API (src/index.ts).
• Added tests and fixtures: a runtime ENS TXT-shape fixture in test/ens.test.ts and ENS-constrained verification cases plus missing-kid checks in test/compat.test.ts.
• No network calls introduced and no production signer hardcoded; ENS fixture is used only for test coverage and examples.

Testing

• Ran build and typecheck with npm run build and npm run typecheck, both succeeded.
• Executed the full test suite with npm test, all tests passed (68 tests, 0 failures).
• New tests exercised ENS TXT fixture parsing and ENS-constrained verification scenarios and succeeded.

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Codex Task