build(skills): clarify pre-merge blocker check heading

Rename "Pre-merge Blocker Check" to "Pre-merge Gate: Blocker Re-check"
and add explicit placement guidance, addressing Copilot review feedback
that the heading didn't match the document's step numbering pattern.
The section is intentionally not a numbered step since it's a gate
between Steps 1-4 and Step 5, not a sequential action.

Author: tylerbutler

.claude/skills/fluid-release/references/minor-release-prep.md

@@ -131,9 +131,11 @@ Create branch `release-prep/<VERSION>/4-bump-<NEXT_VERSION>`, commit, push to up
 
 **Never enable auto-merge on the version bump PR.** Always merge it manually. If a release-blocking PR lands with a new changeset between the release notes merge and the bump merge, you need to revert and regenerate release notes first. Auto-merge creates a race condition where the bump lands before you notice the new changeset, forcing a more complex recovery (downgrading the version on the release branch instead of simply cutting the branch from the right commit).
 
-## Pre-merge Blocker Check
+## Pre-merge Gate: Blocker Re-check
 
-Before merging any of the release-prep PRs, re-check for release blockers. Late-breaking issues can appear between when the PRs were created and when they're ready to merge.
+**Perform this check after Steps 1-4 are complete but before merging any PRs or proceeding to Step 5.**
+
+Re-check for release blockers. Late-breaking issues can appear between when the PRs were created and when they're ready to merge.
 
 ```bash
 gh issue list --repo microsoft/FluidFramework --label release-blocking --state open