Support CLAS trust proof signature union and optional metadata.trace in TypeScript SDK

[GsCommand]

Motivation

• CLAS Trust receipt shape now allows metadata.trace and a union for proof.signature (legacy single-signature or multi-signature array), so the SDK must accept and validate both forms while keeping legacy behavior.
• The TypeScript SDK verifies receipts and the verification logic/tests referenced proof.signature_b64 directly, which breaks new CLAS multi-signature receipts unless guarded.
• Changes should be minimal and preserve backward compatibility for single-signature receipts.

Description

• Added typed support for CLAS proof signatures by introducing SingleProofSignature, MultiProofSignature, and ProofSignature to the TypeScript SDK and exposing three helpers: isSingleProofSignature(), isMultiProofSignature(), and getPrimaryProofSignature().
• Updated verifyReceipt to prefer the new proof.signature primary signature and fall back to the legacy proof.signature_b64 to maintain single-signature compatibility.
• Extended unit tests to cover optional metadata.trace, multi-signature receipts, primary-signature selection, and malformed multi-signature rejection, and added the new helpers to the test harness.
• Files changed: typescript-sdk/src/index.ts, typescript-sdk/scripts/unit-tests.mjs, and typescript-sdk/package-lock.json; no vendored schemas.trust-receipt-v1.json was present in this checkout so the schema file was not modified here.

Testing

• Ran npm install successfully to refresh the lockfile.
• Ran npm test and unit tests passed with 50 passed, 0 failed and template/CLI-smoke checks also passed.
• Ran npm run build and generated artifacts and type declarations successfully (DTS build success reported).
• Ran npm run typecheck (tsc --noEmit) which completed with no errors.

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Codex Task