BReg evidence tutorials: deterministic wording, in-page references, draft link checking, failure guidance

[jeremi]

docs/site/src/content/docs/tutorials/evidence-from-breg.mdx and deploy-evidence-from-breg.mdx:

1. "should contain" and "should produce" describe deterministic output; state what the output is.
2. Five "above" and "below" in-page references across the two pages; name the step instead.
3. Both pages are draft: true, so the built link check never checks their cross-links. Un-draft them once the composition gate is trusted, or run the link check over drafts.
4. Five operationally significant steps lack failure-mode guidance: what a refusal looks like and what to do next.
5. The exported lookup route is POST /v1/records/records:lookup with a JSON body. Check that every GET the pages describe is a direct record read and not the lookup route.

Origin: review of PR #865.