D0.1d Retire old settings storage after the rollback window

[alexeygrigorev]

User direction 2026-09-12: continue the community-base unification of ai-shipping-labs and dtc-website. This issue mirrors plan item D0.1d from community-base docs/plan/phase-0.md; community-base docs/plan/STATUS.md stays authoritative for live status across all four repositories.

Normative references

• community-base docs/plan/phase-0.md, section "D0.1d Retire old settings storage after the rollback window" - the implementation contract; follow its steps literally.
• community-base docs/plan/STATUS.md, row D0.1d - canonical status.
• #355 (D0.1b) - the settings contract inventory and parity proof that define what counts as migrated.
• #364 (D0.1c, merged as 3fb9db07) - the settings cutover whose deployed state this issue retires behind.
• _docs/specs/06-studio-and-admin-api.md and _docs/architecture/app-boundaries.md - docs to update.
• _docs/PROCESS.md, _docs/ci/change-selective-ci.md, playbook P14 (migration rehearsal with counts).

Scope

1. Prove every consumer has moved to the package config app and that audit/history retention holds; unclassified readers block removal.
2. Remove only the inventoried migrated declarations, models and shims, with a storage-drop migration; retain unrelated core primitives and tests, and preserve all parity tests in their owning layer.
3. Update spec 06 and app boundaries to reflect the actual deployed ownership.

Non-goals

• No new settings capability and no package changes; the pinned published release is used as-is.
• No removal of anything outside the D0.1b/D0.1c inventories; a path absent from the inventory is not implicitly safe to delete.

Dependencies and blocked work

• Depends on D0.1c: merged as 3fb9db07 (#364) but its development deploy is currently blocked on the red main CI (Restore the green release matrix: Course creation hits NOT NULL on courses_course.archive_commit_sha #345; lint-mask fix merged as 950065e0, first unmasked run 34676767710 red with fresh traces) and the worker self-check IAM ask (DataTalksClub/aws-infra#49).
• Prerequisite per the plan: the development cutover is green and the rollback window has been explicitly closed. Record both in this issue before implementation starts.

Acceptance criteria

• recorded proof that every consumer moved and audit/history is retained; any unclassified reader blocks removal and is resolved first
• only inventoried migrated declarations, models and shims are removed; unrelated core primitives and tests are retained and parity tests are preserved in their owning layer
• the storage-drop migration is rehearsed on a development copy with counts recorded (P14); uv run python manage.py makemigrations --check --dry-run is clean
• the retired-import inventory is empty except immutable migrations and intentional historical docs
• _docs/specs/06-studio-and-admin-api.md and _docs/architecture/app-boundaries.md reflect the deployed ownership
• the development cutover green evidence and the explicit rollback-window close are recorded on the issue

Scenarios

• Django/integration: migration rehearsal with retained row/audit invariants; site-selected verification per the change-selection plan.
• Browser: not_applicable when the ci/ownership.json graph confirms no render impact; the settings Studio surfaces keep their existing tests.
• Repository/operations: engineer generates the versioned verification plan (make verification-plan VERIFY_ISSUE=<this issue>); tester recomputes it from the frozen base/head; local --no-ff merge; on-call observes CI.

Rollback

• Before the storage drop, reverting the landing restores the retired shims.
• After the storage-drop migration the old tables are gone; the explicit rollback-window close recorded before implementation is the authorization that makes this acceptable.

[alexeygrigorev]

PM grooming report (2026-09-12)

Groomed from the plan section into scope, non-goals, dependencies, testable acceptance criteria and scenarios. needs grooming removed; keeping foundation, P1.

Verified today:

• The plan section D0.1d (community-base docs/plan/phase-0.md) is quoted into the scope; the STATUS.md row is todo and no tracker issue existed for it (tracker searches returned nothing).
• Dependency D0.1c is merged as 3fb9db07 (#364) but its development deploy is still blocked: red main CI (Restore the green release matrix: Course creation hits NOT NULL on courses_course.archive_commit_sha #345; lint-mask fix merged as 950065e0, first unmasked run 34676767710 red with fresh traces) plus the worker self-check IAM ask (DataTalksClub/aws-infra#49, open).
• The plan prerequisite - development cutover green and the rollback window explicitly closed - is an acceptance criterion; both evidences must be recorded on the issue before removal work starts.