Flatten refactor: library/ -> harness/ and library/gen/ -> skills/
opencortex.asd updated with new paths. README.org rewritten with
simplified pitch.
Critical fixes in harness/skills.org (source of truth):
- COSINE-SIMILARITY: Fixed let* binding list paren mismatch
- parse-skill-metadata: Fixed ID extraction block closes
- load-skill-from-org: Fixed handler-case and nested let closes
- def-cognitive-tool :replace-string: Removed extra closing paren
- boot-sequence-tests: Fixed let/unwind-protect nesting
Note: .lisp files are generated from .org via org-babel-tangle at
install time; fixes must always be made in .org and retangled.
Skills derived from opencortex-contrib imported via earlier commits.
