Add skill-dedup regression test for readiness-core #480

Goal

Add a regression test that skill names are deduplicated across skill directories in readiness-core.

Pain source: Community PR #475 fixed double-counting when the same skill existed in e.g. .grok/skills/foo and skills/foo, which inflated the Loop Readiness score.

Files

• tools/readiness-core/test/index.test.mjs (extend)
• Temp fixture dirs created in the test (prefer no permanent multi-dir fixtures unless needed)

Acceptance criteria

• Fixture: same skill directory name under two scanned roots → scanSkillDirectories returns count 1 for that name
• Distinct skill names still count separately
• Documents why dedup matters (score signals skillsOne vs skillsTwoPlus)
• cd tools/readiness-core && npm test passes

Estimated time: ~25–35 minutes · label: tooling

Comment "I'll take this" to get assigned.