Add canonical .ssot registry, ADRs, schemas, and specs

[cobycloud]

Motivation

• Establish a single machine-readable source-of-truth and ship the authored SSOT material under .ssot/ to support deterministic tooling and derived exports.
• Surface stable ID normalization, guard policies, and planning/lifecycle models so release gating and evidence workflows can be automated.

Description

• Add the canonical registry document /.ssot/registry.json with repo metadata, guard policies, document reservations, features, tests, claims, evidence, boundaries, releases, ADR index, and specs.
• Add many ADRs moved/normalized into .ssot/adr/ and new repo-local ADRs prefixed ADR- plus update ADR index references.
• Add JSON Schema artifacts under .ssot/schemas/ including registry.schema.json and snapshot/report schemas and a graph export schema.
• Add human-readable specs under .ssot/specs/ and supportive artifacts including .ssot/reports/upgrade.report.json and updates to MUT.json, README.md, and ADR index docs to reference the new .ssot layout.

Testing

• Performed the registry upgrade/validation step which produced .ssot/reports/upgrade.report.json and reported `

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Codex Task