Add capability registry scaffold and seed entries from reuse-surface

Bootstrap registry/indexes/capabilities.yaml and migrate helix_forge
capability entries owned by this repository for federation publishing.

registry/indexes/capabilities.yaml

@@ -0,0 +1,35 @@
+version: 1
+updated: '2026-06-16'
+domain: helix_forge
+capabilities:
+- id: capability.statehub.progress-log
+  name: Work Progress Logging
+  summary: Record progress events, decisions, and session notes against workstreams
+    and tasks in State Hub.
+  vector: D4 / A4 / C3 / R3
+  domain: helix_forge
+  status: draft
+  owner: state-hub
+  path: registry/capabilities/capability.statehub.progress-log.md
+  tags:
+  - state-hub
+  - progress
+  - coordination
+  consumption_modes:
+  - service API
+- id: capability.statehub.workstream-coordinate
+  name: Workstream And Task Coordination
+  summary: Track active workstreams, tasks, progress, and consistency across domain
+    repositories.
+  vector: D4 / A4 / C3 / R2
+  domain: helix_forge
+  status: draft
+  owner: state-hub
+  path: registry/capabilities/capability.statehub.workstream-coordinate.md
+  tags:
+  - state-hub
+  - coordination
+  - workplans
+  consumption_modes:
+  - service API
+  - HTTP REST