docs(decisions): preserve ADR history and adopt shared review

[szmyty]

Identity #69 starts from eighteen legacy records that claim acceptance but lack canonical metadata and explicit human disposition evidence. This PR preserves that history, makes the gaps reviewable, and installs the shared authoring and advisory validation path.

Changes

• Preserve ADR-004–018 byte-for-byte; extract ADR-001–003 without changing their bodies or old root anchors.
• Add the canonical 21-record index, exact Hygiene policy reference, and eighteen-row migration/disposition packet.
• Reconstruct ADR-019–021 as proposed: immutable release integrity, channel-registry governance, and governed mascot packages.
• Add the exact pinned Aether decision-impact block, PR prompt, Relay advisory workflow, and root continuation checkpoint.
• Keep the current Brand Kit publication configuration and visual baselines unchanged.

Validation

Review head: c035c92976799f3bd62444ef18511818d1d2b5f4. Source checkpoint: 0d36bb4be6702f6329a22a19a4a751d5d28799ae; subsequent commits change only continuity and the validation receipt.

• Native Relay ADR suite: 31 passed, no skips. Separate architecture suite: 29 passed, no skips.
• New proposal schemas/anatomy, policy reference, preservation checks, documentation links and publication configuration checks passed.
• Actual Identity architecture replay: exit 0, nonconformant / warning, 53 warnings (legacy metadata/index/lineage and explicit incomplete adoption).
• Actual ADR collection: exit 2, invalid, partial/current decisions coverage; Hygiene/coverage valid, Observatory normalized, EgoLint invalid; publication denied.
• Hosted advisory evidence: run 38046076510 succeeded at prior branch head 7cc7d4d0956d728c0bcf2c4ba164eaa0409710a2, representing PR merge candidate 3a6c513a6779d51ac8c3b61de9678bde12759d6d. Actual upload and final advisory enforcement succeeded; the retained artifact preserves nonconformant/warning, 53 warnings. ZIP SHA-256 daf9a076ee77e1cc2bd95b9204744ca71a3503e4513735fac7607b3f0f96cc56 and all archived checksums were verified; retention expires 2026-11-09T10:47:36Z. This is execution/retention evidence, not corpus conformance. Latest-head c035c92976799f3bd62444ef18511818d1d2b5f4 decision validation and Identity CLI validation both succeeded. Current-head artifact download/checksum inspection is not claimed; the independently verified retention evidence above remains bound to its stated prior head.
• Production Decisions build, deployment and live-route acceptance remain incomplete.

This is a migration checkpoint, not complete corpus conformance. Refs #69; it must remain open.

Human disposition and continuation

Review the concrete packet. Hygiene's pinned migration rule requires explicit retain/correct/supersede choices for the eighteen legacy acceptance claims. Merge alone supplies no ADR ratification. The three new proposals require their own disposition.

After those decisions: preserve original history while adding canonical metadata/anatomy, rerun source validation, then review the shared production Decisions artifact and its explicitly owned host/composition/deployment.

Decision impact and rollback

Operation: create ADR-019–021 as proposed; reference egohygiene/hygiene#ADR-002 for the migration and validation adoption. No new policy or publication authority is introduced. Roll back through a scoped reviewed revert, preserving later authored history and existing release/deployment rollback points.

Canonical program log: egohygiene/.github#30