feat: skill hygiene validator [OMN-5200]

[jonahgabriel]

Summary

• New cross-repo validator scripts/validation/validate_skill_hygiene.py with 7 checks enforcing skill directory naming, structure, and Python separation
• Follows check_ai_slop.py pattern: standalone script, argparse CLI, exit codes 0/1/2
• --strict mode promotes migration warnings (M1: Implement Pydantic schema models v1 (Day Close + Ticket Contract) #4 skill-md-required, feat(export): implement JSON schema export script (OMN-963) #5 name-matches-dir) to errors for post-migration CI
• 34 unit tests covering all checks, strict mode transitions, CLI, and integration scenarios

Checks

#	Check	Default	Strict
1	underscore-names	ERROR	ERROR
2	no-duplicate-names	ERROR	ERROR
3	no-unindexed-nesting	ERROR	ERROR
4	skill-md-required	WARNING	ERROR
5	name-matches-dir	WARNING	ERROR
6	no-python-in-skills	ERROR	ERROR
7	no-orphan-topics	WARNING	WARNING

Test plan

• uv run pytest tests/test_validate_skill_hygiene.py -v — 34/34 passing
• Validated against real omniclaude skill tree — correctly detects all kebab-case violations
• Pre-commit hooks pass

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: e4d2cd36-01ef-4a8c-a781-e2f3f66ddbba

📥 Commits

Reviewing files that changed from the base of the PR and between 3c7f8f1 and df0f075.

📒 Files selected for processing (2)

• scripts/validation/validate_skill_hygiene.py
• tests/test_validate_skill_hygiene.py

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch jonah/omn-5200-skill-hygiene-validator

📝 Coding Plan

• Generate coding plan for human review comments

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