RFC 8417 ships prose example figures rather than machine-readable test
vectors and defines no external conformance suite, so the library's
conformance story is internal golden fixtures driven through the full
consumer/producer cycle. This lands that suite: four claims-set fixtures
under testdata/ and a table-driven test that exercises each one.

The canonical fixture, scim_create.json, is transcribed verbatim from
the RFC 8417 §2.1 SCIM provisioning example: iss, iat, jti, a two-member
aud array, and a single SCIM create event. The remaining three are
labelled synthetic in testdata/README.md and use RFC 2606 example
domains: minimal.json is the smallest SET satisfying the §2.2 MUSTs (one
event with the empty-object payload); txn_toe_subid.json exercises txn,
a toe distinct from iat, an RFC 9493 iss_sub sub_id, and an aud array;
single_aud.json carries a bare-string aud and an event a registered
decoder turns into a typed value. No non-spec event vocabulary is
presented as if it came from the RFC.

For each fixture the test parses the bytes, asserts the decoded SET
fields, confirms Validate accepts it, decodes events through the
registry (one registered URI to a typed value, the rest left raw), and
Encodes it back. It then pins byte-stability two ways: every event
payload appears in the Encode output in its canonical compact form with
member order preserved — the property json.RawMessage buys over
map[string]any — and Parse → Encode → Parse is a fixed point. The
registry decoder is wired once in init rather than a test body so it
survives -shuffle and -count without a duplicate-registration panic.

No library code changes; fixtures and tests only. These run under the
existing test CI job.

Co-Authored-By: Claude <noreply@anthropic.com>