docs(release): SKILL.md Step 7 restates two helpers' decision predicates

Summary

Advisory findings from #455's review round, deferred rather than folded (no blocking round was open; rules/review-severity.md Split Reading From Acting).

Two Step 7 bullets in skills/release/SKILL.md restate a helper's Boolean predicate, which rules/script-as-black-box.md "What Skills Do Not Restate" reserves for the script:

1. SKILL.md:194 — restates verify-publish-landed.sh's conjunction (conclusion == success AND Latest Version > PRE). Keep the invocation and the exit/output contract; point through PUBLICATION.md to the script header for the predicate.
2. SKILL.md:200 — restates verify-github-release.sh's conjunction of run success, release existence, publication status and retrievable assets. Same treatment.

Presentation-only: no agent behavior changes either way, which is why neither gated.

Test plan

• Neither bullet names a predicate; both name the command and where its contract lives
• PUBLICATION.md still carries each helper's exit-code contract, so nothing is lost by the cut

Start with rules/script-as-black-box.md and inspect Step 7 in skills/release/SKILL.md around lines 194 and 200. Check the headers of verify-publish-landed.sh and verify-github-release.sh, then review PUBLICATION.md for their exit-code contracts. Done means both bullets invoke the commands without restating predicates and still point to the documented contracts.