~/dev/skills/skills/boss/ was visually awkward (skills/skills
read twice) and structurally unnecessary — the skills ARE the
repo's main content, not a sub-collection inside it.
Layout changes:
- boss/SKILL.md moves to the repo root
- skills/README.md (migration notes) moves to docs/migration.md
where documentation-about-the-system belongs
- install.sh discovers skills via the SKILL.md marker file
instead of a hardcoded skills/<name>/ path, so future skill
additions just drop in at the root
Cross-references in boss/SKILL.md (../README.md, ../brainstorm,
etc.) now resolve against the repo root instead of the old
skills/ subdir, which is what they describe: top-level
README is the skill table; sibling skill dirs are the other
migrated skills.
