test: add policy-service coverage and related service tests

[mariana-andruk-qa]

Summary

Adds unit and contract test coverage for policy-service, plus a couple of related tests in guardian-service and api-gateway.

• policy-service: unit tests for block validators, blocks, helpers, decorators, errors, and policy-engine utilities, plus V8/c8 coverage tooling (run-coverage.mjs, coverage-report.mjs, COVERAGE_NOTES.md) and a block-about contract test.
• guardian-service: new build-documentation-urls helper with accompanying unit tests.
• api-gateway: dmrv service test (alias resolution) using esmock.

Test results

Run against freshly built dist/ output:

Service	Passing	Failing
api-gateway	12	0
guardian-service	16	0
policy-service	1195	12

Known failing policy-service tests (12)

These are included as-is and still need follow-up; they are not import/setup regressions in unrelated code:

• 3× require an initialized ORM (PolicyValidator.build() ×2, SchemaValidator property test) — fail with "ORM is not initialized" in a pure unit context.
• 2× PolicyValidator assertions expect true/false but the implementation returns the validator object.
• 2× CommonBlock-delegating validators (TransformationUIAddon, HttpRequestUIAddon) expect no errors for empty options, but the validators correctly report required-field errors.
• 5× PolicyUtils helpers: getDocumentType returns VerifiableCredential/DID (tests expect vc-document/did-document); createVP/createVC set status to 0 (tests expect NEW).

Notes

• yarn.lock changes were intentionally excluded (unrelated dependency churn).