docs(#771): close role split rc.8 residuals

docs/scratchpads/771-kbn101-db-role-split.md

@@ -96,3 +96,12 @@ Independent Codex review found two blockers and security review found two medium
 - **Plan:** (1) make the finite DDL/static-bypass inventory and `DATABASE_URL`-only denial matrix exact, including the runner-prepared persistent pgvector fixture and migrated two-gateway harness; (2) freeze executable `public`-to-`mosaic` and `mosaic_extensions` transition, Drizzle ownership, object-catalog classes/order, eligibility and rollback tests; (3) bind repository/control-plane ownership, UID/GID validation, exact artifact/mount rules, and both gateway TLS topology; (4) correct PRD acceptance mapping and cross-document rc.7 status; then run formatting, link/contract, source-path, diff, review, commit, queue guard, and push.
 - **Independent review closure:** initial Codex review found Gateway-key consumer wording, `CLAUDE.md` omission, final schema-owner set, and placeholder SANs; all are now explicit. Re-review found the legacy `0001` vector-type resolution problem and `docs/federation/SETUP.md` raw-DDL instruction; the legacy runner now uses only its fixed non-writable `pg_catalog,public,mosaic_extensions` history path, while runtime remains `pg_catalog,mosaic`, and the federation setup path is assigned to KBN-101-07/static inventory. Security review final verdict: no confident vulnerability. The review also repeated the pre-existing tracked `.mosaic` session-state concern; it remains deliberately unstaged/excluded by this task.
 - **Completion evidence:** changed Markdown is Prettier-formatted; local links and strict native-kanban TypeScript passed; source-path inventory confirmed all current referenced paths (the new `apps/gateway/Dockerfile` is explicitly a planned KBN-101-05 artifact); diff check and authorized-doc allowlist passed. No source-code TDD applies to this documentation-only remediation.
+
+## 2026-07-15 — rc.8 exact residual remediation session
+
+- **Objective / correction:** Close all three HIGH findings in the independent rc.7 exact-head re-review at `/home/hermes/agent-work/reviews/771-kbn101-contract-rereview2-0778eba.md` for `0778eba2db3c2dfbaca3af352b12ba0389d3552b`. Scope remains documentation-only: no source, config, Compose, CI, deployment, secret, or migration artifact changed; pre-existing `.mosaic/orchestrator` state remains excluded.
+- **Finite authority closure:** KBN-101-06 now classifies exact current source/scripts/package bins, operator docs, and deploy manifests. `packages/db/src/index.ts` has explicit removal/compile-import negative ownership; `docs/fleet/backlog-conventions.md` and `docs/PERFORMANCE.md` now remove first-use/direct-Drizzle/Gateway-startup migration instructions and point to sole runner/readiness. Byte-immutable historical SQL, PGlite-only routines, negative-test literals, vendored/generated artifacts, and labeled historical reports are exact-path/category reviewed allowlists; unknown hits fail. The contract explicitly rejects relying on a naive token scan alone.
+- **Executable and exclusive handoff closure:** KBN-101-03 exclusively owns the published `mosaic-db-migrator` bin, `packages/db/src/cli.ts`, private migrator modules, `docker/db-migrator.Dockerfile`, exact `--run|--verify|--help`, environment/argv limits, sanitized exits, and command/order tests. KBN-101-00 exclusively owns `infra/pg-bootstrap/roles.sql`, `infra/pg-bootstrap/extensions.sql`, `infra/pg-bootstrap/README.md`, and bootstrap tests. KBN-101-05 exclusively owns `tools/db/render-postgres-secrets.ts`, its tests, and deployment declarations, consuming the versioned bootstrap interface without overlap.
+- **pgvector owner closure:** `mosaic_extension_owner` is dedicated NOLOGIN, available only to the external bootstrap actor during bootstrap; fresh vector/member ownership remains there. The contract records PostgreSQL's unsupported extension-owner transfer and forbids catalog mutation, ownership adoption, and `DROP CASCADE`. Approved-owner existing extensions use verified `ALTER EXTENSION ... SET SCHEMA`; legacy runtime-owned extensions fail closed to a controlled backup/shadow/runner/copy-evidence/quiesce/final-delta/atomic-switch/read-only-rollback migration. It requires `pg_extension.extowner`, member/schema/version, and runtime/migrator/schema-owner ALTER/DROP/member-update denial tests across clean, approved-owner, legacy shadow, partial/resume/rollback, and N-1.
+- **Cross-document state:** PRD, KBN contract, shared contract, task decomposition, index, sitemap, current operator docs, and this scratchpad are rc.8-consistent. The only intended next action is a fresh independent exact-head re-review after validation/push.
+- **Validation / review:** Prettier passed for all nine changed Markdown documents; local links passed (9 documents); `pnpm exec tsc --noEmit -p docs/native-kanban-sot/tsconfig.json` passed; source-path inventory passed (20 paths: 8 current, 12 explicitly planned); finite-authority requirement checklist and `git diff --check` passed. Manual documentation/security review checked the three requested paths, private-only runner boundary/exit contract, non-overlapping 00/03/05 ownership, extension-owner denial and shadow path, and `.mosaic` exclusion. No source-code TDD applies because this is contract-only remediation. Next: stage authorized docs only, commit, queue guard, push, and verify remote exact SHA; then await a fresh independent exact-head re-review.