prose-pointer-lint-must-resolve-from-skills-root-not-skill-dir

When the fusion-invariants lint was extended to catch dead prose pointers (`docs/X.md` references), it initially resolved paths relative to each skill’s own directory, causing 10 false failures for governance docs stored at /root/.claude/skills/docs/. Fix: the lint must check both skill-local docs/ AND the skills-root docs/ directory to correctly resolve cross-skill governance document references.