docs(plans): refactor-to-next merge plan and lead decision 66 (sage)

Jason's 2026-10-08 rulings via Mos (thread 1eba59e5). R10: next stays
the trunk; the plan pins refactor b8db39cf and next 2101c9b4, finds a
clean merge-tree, and names the CI gate, approval identity, frozen
next-lane publishing, root .mosaic/repo.json, 13 stale v1 PRs and the
hardcoded ledger branch as the work. Nothing merged.

R8: Path A on the new estate Vikunja meets slice 1 and replaces
decision 61's Path B. The runbook's Path A text names the estate
instance and the share-only isolation rule.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/guides/slice-1-identities.md

@@ -106,11 +106,21 @@ that is yours.
 
 ### Path A, an existing instance
 
+Mosaic Stack uses this path on the estate instance (lead decision 66).
+Set `VK` to its HTTPS base URL. Don't use tasks.setspark.io.
+
 Check that `curl -s "$VK/api/v1/info"` reports `v2.7.0` or later. Use your
 existing account as the owner.
 
+The estate instance also holds Launchpad, personal and system projects.
+A bot sees only the projects shared with it, so section 3 shares the
+`mosaic-stack` project and nothing else. Never share another project
+with a `bot-mosaic-stack-*` user.
+
 ### Path B, the bundled instance
 
+Other installs can use this path. Mosaic Stack's own install doesn't.
+
 Row S3 ships `packages/tasks/deploy/vikunja/` for this. Until it lands,
 these commands start the same pinned image the probes used, bound to
 127.0.0.1: