Dead allowlist pattern + dead sweep in /retro #2552

Evidence: retros/*.md pattern matches nothing /retro writes (wrong dir + ext: .context/retros/*.json, ~/.gstack/retros/global-*.json); retro/SKILL.md:108 quotes a tilde inside [ -x … ] so the orphan sweep never runs. (v1.62.0.0, d078622)

Class: two one-line fixes, same skill