Audit templates/spawn-ui-rename.md extraction mechanics against trailer-template structure

Quick pre-flight validation before the rename template's first live use. The trailer template (templates/spawn-commit-trailer.md) has held 4 nights since its June 10 ship and uses an awk-based literal-block extractor that the spawn-prompt builder cat's verbatim. Acceptance: 1. cat the Literal block section from templates/spawn-ui-rename.md (using the same awk markers as the trailer template) 2. Verify the output is plain text suitable to cat into a sub-agent spawn prompt (no surrounding doc text, no markdown that would confuse the sub-agent) 3. If the structure differs from the trailer template's, normalize it 4. Add a one-liner test in templates/ that verifies extraction (could be a 5-line shell test) Reference: LEARNINGS 2026-06-14 carry-forward priority 7. Same shape as the post-ship validation pattern from the source-of-truth-rule helper (bin/standup-build-asks.sh acceptance test 2026-06-12).