Archive superseded docs, clarify verification flows, and update pack registry

[SDL-HQ]

Motivation

• Consolidate historical/superseded review documents under docs/archive/ to make current guidance explicit and avoid accidental use of outdated material.
• Clarify local vs published certificate and ITGL workflows so operators understand which files are produced locally (proofs/local-audit.json) and what verification steps produce proofs/itgl_final_hash.txt.
• Narrow the public/registry surface for packs by marking non-ready packs as draft/internal so sir packs list and registries reflect intended availability.

Description

• Added docs/archive/README.md and moved historical design/review docs into docs/archive/ (d5, d11, d12), and updated all references to point to the archive path where applicable.
• Bumped the top-level README version string to 2.2.0 and added SECURITY.md and docs/archive/README.md links into the Guides list.
• Updated multiple docs (assurance-kit.md, engineer-guide.md, evaluator-technical-explainer.md, minimal-pilot-runbook.md, and others) to clarify that local certificate generation writes proofs/local-audit.json, that proofs/itgl_final_hash.txt is produced by ITGL verification (not sir run), and to state contract vs signature verification semantics.
• Modified RETENTION.md to include docs/ in the set of retained artifacts and adjusted evidence/retention wording for clarity.
• Revised spec/packs/pack_registry.v1.json to mark several example packs as `

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Codex Task