test(okf): capture block-form fixture and collection baseline before any decoder

Co-Authored-By: Claude <claude-opus-5>

tests/golden/block-form-provenance/bundle/attested.md

@@ -0,0 +1,19 @@
+---
+type: concept
+okf_version: 0.2
+title: "Attested computation"
+generated: { by: process:fixture-author, at: 2026-09-02T00:00:00Z }
+verified:
+  - { by: process:fixture-check, at: 2026-09-02T08:00:00Z }
+sources:
+  - resource: https://example.invalid/fixture-cost-baseline
+    id: fixture-cost-baseline
+---
+
+One verification event, written as a single-entry block sequence — the SPEC-canonical
+long form of `verified: { by: ..., at: ... }`. The actor is a `process:` one, so the
+trust tier a consumer derives from it is machine-confirmed, never human-reviewed.
+
+`sources` is written in block form too, so a reader that only understands the flow
+shorthand loses the provenance of this concept entirely rather than reporting that it
+could not read it.