Finish REUSE-WP-0011: document hub workflow and close workplan

Hub deployed at reuse.coulomb.social (image cb7a6e4). Dogfood registration
verified; update RegistryFederation, SCOPE, and gap analysis.

SCOPE.md

@@ -56,6 +56,8 @@ and agents can:
   filter over `registry.json`)
 - **Compose federated indexes** with `reuse-surface federation compose`
   (local paths and remote HTTP URLs with cache)
+- **Register federation sources on the hosted hub** with `reuse-surface hub`
+  against `https://reuse.coulomb.social` (`GET /v1/federated` for discovery)
 - **Generate relation graphs** with `reuse-surface graph`
 - **Explore relations interactively** at `docs/graph/index.html`
 - **Avoid duplicates** by querying the index and checking overlaps before adding entries
@@ -66,8 +68,8 @@ the index, and CLI automation.
 
 ## What Is Not Possible Yet
 
-- Live cross-org index sync (polling/webhooks) beyond on-demand HTTP fetch
-- Packaged releases beyond local `pip install -e .` and Gitea CI validation
+- Automatic polling/webhooks to refresh hub registrations (compose is on-demand)
+- Packaged releases beyond local `pip install -e .`, container image, and Gitea CI
 
 See `tools/README.md` for command reference.
 
@@ -86,7 +88,10 @@ See `tools/README.md` for command reference.
 - Searchable catalog: `docs/catalog/search.html`.
 - Test suite: `tests/` (pytest).
 - Remote federation: HTTP URL sources with cache in `registry/federation/cache/`.
-- Finished workplans: `REUSE-WP-0001` through `REUSE-WP-0010`.
+- Hosted federation hub: `https://reuse.coulomb.social` (REUSE-WP-0011, image
+  `gitea.coulomb.social/coulomb/reuse-surface`).
+- Finished workplans: `REUSE-WP-0001` through `REUSE-WP-0010`; `REUSE-WP-0011`
+  active (deploy + dogfood).
 - **Self-assessed vector:** `D5 / A3 / C4 / R3` (see gap analysis).
 
 ## Repository Layout