refactor: consume WolfXL's versioned Guard contract

[wolfiesch]

Summary

Turn spreadsheet-guard into a genuinely thin package/CLI identity over WolfXL's canonical Guard contract:

• load only wolfxl.guard_contract, not the internal wolfxl.operations module;
• pin wolfxl-guard-contract-v1 and reject missing, older, or malformed runtimes before executing;
• delegate policy, inspection, schema/status validation, and report/artifact binding to WolfXL;
• retain only package-specific availability errors, the small GuardOutcome facade, and CLI exit behavior;
• add independent Python 3.11/3.13 package, Ruff, Mypy, test, and wheel-build CI.

Dependency

Depends on SynthGL/wolfxl#581. Keep this PR draft and merge it only after that producer contract is available in the distributed WolfXL runtime.

Verification

• 11 focused tests pass, including malformed scalar/container result statuses.
• Exact-head CI run 33349242254 passes on Python 3.11 and 3.13 (Ruff, strict Mypy, tests, wheel build).
• Tests prove exact contract-version rejection and fail-closed malformed-result handling without requiring a proprietary runtime in this public repository.

No package was published and no external outreach was performed.

---

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[wolfiesch]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-31T02:02:34.472291Z	ccc9b32	Manual request

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 8100b6ab74

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[wolfiesch]

@codex review

Please review exact head fd6a84728f32e8435d405f173b23f6328b107643.

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: fd6a84728f

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[wolfiesch]

@codex review

Please review exact head ccc9b32ab1541c5a7e464561c780833df21daa01, which additionally rejects non-text Guard result statuses fail-closed.

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Breezy!

Reviewed commit: ccc9b32ab1

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