sage: row 171 brief cites mos-0854 (D1 withdrawn, option B approved) in place of its open decision section (#1668)

docs/plans/2026-10-19_project-names-and-repos.md

@@ -1,27 +1,18 @@
 # Brief: a thread project named like a business-file repo
 
-P19 379, Gitea #1668, queue row 171. This brief comes from Mos's finding F2 in the 8e7ea89a1 window (mos-0844) and
-Mos's ruling mos-0845 D1. Owner Rocko, reviewer Dewey, gate owner Sage. Line numbers are at origin/refactor 42817065e.
+P19 379, Gitea #1668, queue row 171. This brief comes from Mos's finding F2 in the 8e7ea89a1 window (mos-0844), with
+the design ruled in mos-0854. Owner Rocko, reviewer Dewey, gate owner Sage. Line numbers are at origin/refactor 42817065e.
 
-## Decision needed first: this brief departs from D1
+## Decision
 
-mos-0845 D1 gave a go to the "one-registry design" in Sage's F2 recommendation: the bus lists the business file's
-projects in `project.list`, and `thread.create` accepts their ids. When Sage wrote that recommendation, Sage hadn't
-checked three things, and each of them is a reason against it:
+Mos's mos-0854 withdrew mos-0845 D1 (one registry) and approved the design below (option B in sage-1017). The reasons:
+- PRD 1.2 (`docs/prd/mosaic-stack.md:726-730`) calls the business file's `projects` git repositories and keeps them
+  apart from REQ-ORG-2 thread projects. Row 121 linked the two by `repo` (`packages/bus/src/broker.mjs:2244-2245`).
+- REQ-THREAD-2 (prd:673-678) has users create projects, and only Jason edits the business file.
+- `threads.project` references the store's `projects` (`packages/bus/src/migrations/3d-3e.sql:17`).
+Renaming the business-file key to `repos` isn't filed. That's a schema change for Jason, and nothing needs it yet.
 
-1. PRD 1.2 (`docs/prd/mosaic-stack.md:726-730`) says the business file's `projects` key names git repositories to
-   clone, while a REQ-ORG-2 project is the user's container for threads. Row 121 kept the two apart and linked them by
-   `repo` (`packages/bus/src/broker.mjs:2244-2245`: "`repo` names a project from the business file; the rename to repos
-   is a P19 follow-up").
-2. REQ-THREAD-2 (prd:673-678) has the user create projects from the CLI or the WebUI. Only Jason edits the business
-   file, so if the business file were the registry, users couldn't create projects at all.
-3. `threads.project` is `REFERENCES projects(id)` (`packages/bus/src/migrations/3d-3e.sql:17`). Accepting
-   business-file ids in `thread.create` would need a schema migration, a re-pin with `--migrate` and downtime.
-
-Sage recommends option B below in place of D1's one-registry design. Mos rules on it. If Mos keeps D1, this brief gets
-rewritten as a schema and PRD change for Jason, and none of the B text below applies.
-
-## Option B: keep the two apart and close the name trap
+## Keep the two apart and close the name trap
 
 ### The problem B fixes