docs(zi): accept protected main and signed milestones

[ss-o]

Summary

Accept ADR-0039 for Zi integration on protected main with full stable qualification before delivery and separately authorized signed milestone tags. Canonical branch, release and testing guidance describes the conditional transition, with generated consumers regenerated from their declared knowledge sources.

ADR-0039 records acceptance by ss-o. ADR-0019 and ADR-0028 retain their accepted historical contracts until verified cutover. The accepted migration preserves existing main installers and self-update, review gates, protected history and signed-tag authorization; acceptance does not claim that the cutover is already complete.

Refs #772. Part of #771; implementation is tracked in z-shell/zi#628 and staged in z-shell/zi#629.

Verification

• Passed python3 -m unittest automation/governance/test_decision_records.py automation/knowledge/test_knowledge_delivery.py automation/agents/test_validate_agent_policy.py -q: 130 tests.
• Passed knowledge coverage (359 files), delivery checks (56 consumers), automation/agents/validate-agent-policy.py, automation/agents/org-routing.py validate and git diff --check.
• Hosted checks and review of record remain pending. The coordinated Zi changes passed 43 local Zsh test files; hosted cross-platform qualification and live protection replacement are not yet verified.

Agent handoff

• Status: Ready for review; migration incomplete.
• Current state: Accepted ADR, conditional canonical policy and generated consumers are ready. The existing branch and promotion decisions remain operative until verified cutover.
• Blockers: Current-head checks and review of record; qualification and enforcement cutover remain pending.
• Next steps: Review alongside ci(release): stage main qualification and signed milestones zi#629, deliver staged qualification through the existing promotion path, verify the exact main SHA, then coordinate ADR acceptance, protection replacement, historical issue reconciliation, downstream documentation and metadata, and separately authorized branch retirement.
• Related tracker/issues: chore(governance): migrate Zi to protected main integration #771, docs(governance): define Zi main integration and milestone authorization #772 and chore(ci): qualify ordinary main PRs and separate milestone publication zi#628 in Z-Shell Delivery (Project 28).

Instruction impact

1. This changes shared branch policy, scoped release/testing guidance and the decision inventory. Live enforcement is a later cutover step.
2. Organization-guided runtimes, Zi contributors and release maintainers receive the applicable guidance. The private workspace consumer requires synchronization after public delivery; runtime adapters do not change.
3. Canonical owners remain knowledge-domain sources for generated guidance and decisions/ for ADRs. Generated consumers are regenerated.
4. ADR-0019 and ADR-0028 remain operative until verified cutover. ADR-0039 states that boundary explicitly so accepted migration policy does not imply completed enforcement.
5. The organization manifest adds an advisory ADR-0039 route; mandatory policy still arrives through existing routes. No runtime-specific route is required for the advisory record.
6. Complete generated AGENTS.md and runbooks carry the transition without optional hooks or skills. Manual runtime discovery remains unverified.
7. Coverage, generated delivery, policy/routing validation and 130 affected tests pass. Private consumer regeneration remains a downstream delivery step.

[ss-o]

Fallback review under ADR-0026: Copilot request not registered on b097a91

No confirmed blocking defects found in the full policy diff at b097a91ec245f4e91beb9bb54fc148222af66352, against base and merge base 362528e9a9c5b802f4b8b1014473f531d3151a58.

Note

This is a self-review, not independent approval. ADR-0039 records acceptance by ss-o; verified operational cutover remains separate.

Evidence

• Decision authority and preservation: passed. ADR-0039 is ACCEPTED with ss-o as decider under explicit maintainer acceptance. ADR-0019 and ADR-0028 retain their accepted records and remain operative until verified cutover. Supersession is conditional and historical promotion ancestry is retained.
• Policy correctness: passed. Full qualification moves before ordinary main delivery; installation and self-update stay on main. Milestone tags retain a separate exact-SHA authorization boundary. The ordered cutover preserves review, signatures, resolved threads and protected history; it requires hosted proof before removing the source guard or retiring next.
• Canonical ownership and generation: passed. Shared agent, release and testing guidance is edited in knowledge-domain sources. Delivery regenerates complete consumers, and the decision-index generator reflects the accepted status and decider. Coverage declares the new ADR, and its advisory route does not silently introduce enforcement before cutover.
• Instruction impact: passed. The PR body answers all seven required impact questions. Runtime-specific adapters do not change. Private consumer synchronization and manual runtime discovery are explicitly downstream or unverified.
• Validation: passed. All 130 affected decision, knowledge-delivery and policy tests pass after acceptance. Knowledge coverage/delivery, decision-index, policy/routing and whitespace checks pass. Current-head hosted checks must be green before merge.

Limits and follow-up

Acceptance chooses the migration; it does not assert that Zi main has the replacement required contexts or that next is retired. Coordinate zi#629 and the remaining zi#628 proof/cutover work. Private consumer synchronization and downstream documentation remain delivery dependencies. Parent #771 and policy #772 stay open because this PR references rather than closes incomplete migration work.

All current-head hosted checks passed. The configured Copilot request returned no requested reviewer and no new timeline event naming Copilot; cause unconfirmed. The maintainer elected the Class 4 fallback for this exact head. No review threads were present.