codex/pr132-foundational-ci (#139)

- **proofs(lean4) + tests: A-12 path-traversal containment**
- **ci: realign validation matrix with current support**
- **ci: build lean wrapper without make**
- **ci: provide rust sources for fuzz builds**

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath