Adds the 8 already-copied engineering skills (ask-matt, codebase-design,
domain-modeling, implement, prototype, resolving-merge-conflicts,
setup-matt-pocock-skills, triage) plus frontend-design to
engineering/README.md and plugin.json. Also rewrites misc/README.md,
which listed 3 skills with no matching folder and was missing 3 real ones.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
broesmel