Add optional metadata.trace to receipts and extend shared proof schema

[GsCommand]

Motivation

• Add optional metadata.trace to trust receipts to support distributed trace correlation without breaking existing receipts.
• Extend the shared proof envelope to accept both json.sorted_keys.v1 and erc8211.merkle.v1 canonicalizations and to support solver-style multi-signature proofs while remaining backward compatible with single-signature proofs.
• Resolve schema resolution during validation and add automated checks to ensure both legacy and new proof/trace shapes validate as intended.

Description

• Updated 10 receipt schemas under schemas/trust-verification/*/*.receipt.schema.json to include an optional metadata.properties.trace with "$ref": "../_shared/trace.schema.json" while keeping metadata.required as ["proof"] and metadata.additionalProperties: false.
• Modified schemas/trust-verification/_shared/proof.schema.json to change canonicalization from a const to an enum allowing json.sorted_keys.v1 and erc8211.merkle.v1, and changed signature to a oneOf that accepts the existing single-signature object or a multi-signature array where each entry requires a role from the allowed set.
• Added schemas/trust-verification/_shared/trace.schema.json (a local copy/reference) to ensure receipt-local ../_shared/trace.schema.json references resolve during validation without altering the original schemas/trust/_shared/trace.schema.json.
• Extended the validator script scripts/validate-trust-verification-examples.mjs to load the trace schema and to run explicit schema checks for single-signature + json.sorted_keys.v1, erc8211.merkle.v1 + signature array with role, metadata with proof only, metadata with proof+trace, and rejection of unknown extra metadata fields.

Testing

• jq parsing check over all modified JSON files succeeded (no JSON syntax errors).
• npm test (runs node scripts/validate-trust-verification-examples.mjs) passed and reported all trust-verification example validations and the new schema checks as PASS.
• npm run build and npm run typecheck are not available in this repository (missing scripts) and were therefore not executed.

Files changed: 13 (including schemas/trust-verification/_shared/proof.schema.json, schemas/trust-verification/_shared/trace.schema.json, 10 receipt schemas under schemas/trust-verification/*/*.receipt.schema.json, and scripts/validate-trust-verification-examples.mjs).
Receipt schemas updated: 10.
Request schemas, OpenAPI files, and MCP tool files were not modified.

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Codex Task