/simplify-code findings on the salvage stack:
- extract _category_skill_dirs() as the single category detector; the
install guard and hermes_cli._existing_categories() now share it
(third copy of the heuristic eliminated)
- filter rglob hits through is_excluded_skill_path so vendored /
support-dir SKILL.md files (node_modules, references/pkg) no longer
misclassify a plain directory as a category and block install
- fix inaccurate WHY comment (lock-file check only guards hub-installed
skills, not hand-authored dirs), drop underscore prefixes on locals,
fold the file-collision guard under the single exists() check
0f2da9687f