test(19.4-04): unit tests for wristband's OIDC flavour
- PHP protocol cases, one subtest per PHP method: TestPKCEVerifier,
TestRedirectURIMatch, TestTokenIssuer, TestAuthCodeLifecycle,
TestPKCEAndReplay, TestConsentCSRF (cases 1-5)
- Go-only behaviour: discovery bytes, JWKS shapes, PEM parsing, ES256 and
mixed rings, validation order, repeated parameters, PHP encoding,
resume, switch account, JSON consent, client authentication, uniform
userinfo 401, pairwise subjects, opt-in refresh, kind isolation,
flavour dispatch, SetOIDCBackend checks, MCP refuses openid
- every name required by the gate's go stage