DCQL: keep the verifier's error in the failure message

[scott410md]

What it does

When a presentation or a credential fails verification during DCQL evaluation, the record's errors get a failure line such as:

Presentation for <credential id> failed verification

If the verifier's result payload carries an "error" text (for example a status list result), that line now ends with ": <error>":

Presentation for <credential id> failed verification: Credential is revoked or suspended (status_list idx=1, status=1)

The same applies to the Credential for <credential id> failed verification line.

The line is unchanged when there is no error text: no "error" key, an empty or non-string value, or a payload that is not a dict.

Why

A failed presentation record says why it failed. Callers that show a reason to a user, for example a verifier dashboard, can show the verifier's own text instead of a generic failure.

Scope

• oid4vc/oid4vc/dcql.py only. A small helper, _with_verifier_error, is used for the presentation and credential failure lines.
• No API change, no record schema change and no dependency change.
• Successful verification is unchanged.

Tests

There are six new cases in oid4vc/oid4vc/tests/test_dcql.py. They use mocked verifiers and check the failure line for:

• a presentation failure with an error text (the line ends with ": <error>");
• a presentation failure without one (the line is unchanged);
• a presentation failure whose payload is not a dict (the line is unchanged);
• the same three cases for a credential failure.

Results on this branch:

• pytest oid4vc/tests/test_dcql.py: 9 passed (3 existing, 6 new).
• pytest jwt_vc_json mso_mdoc oid4vc sd_jwt_vc: 313 passed (307 on the base commit, plus the 6 new cases), 0 failed.
• ruff check and ruff format --check (ruff 0.15.7, repository configuration) on both files: clean.

Companion change in proven-core (stores these errors with the presentation) will follow as a separate draft PR on main-2.0.

[scott410md]

Companion proven-core PR (stores these errors with the presentation): https://github.com/Indicio-tech/proven-core/pull/528