docs: establish state hub baseline

workplans/README.md

@@ -0,0 +1,24 @@
+# State Hub Workplans
+
+New workplans in this repository use:
+
+```text
+SHUB-WP-0001-short-title.md
+```
+
+Workplan frontmatter should include:
+
+```yaml
+id: SHUB-WP-0001
+type: workplan
+title: "Short Title"
+domain: custodian
+repo: state-hub
+status: active
+owner: custodian
+topic_slug: custodian
+```
+
+During extraction, legacy `CUST-WP-*` plans may be bridged or migrated with
+their existing `state_hub_workstream_id` values. Write files first, then run
+State Hub consistency sync after this repo is registered.