setup piped doc generation through `tail -3`, so a generator crash kept the
pipe's exit 0 and installs completed "successfully" with broken or missing
SKILL.md files. Capture the real exit status at BOTH sites (the main
gen:skill-docs step and the gbrain-detected gen:skill-docs:user regen —
the second drifted in after the PR and its own test caught it), print the
tail for UX, and fail loudly.
Contributed by @DavidMiserak (PR #1898; VERSION/CHANGELOG collateral
stripped; extended to the second pipe site).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>