Add State Hub bootstrap workplan and agent integration files

Seed workplans/ with bootstrap workplan to satisfy ADR-001 C-01.
Includes regenerated dev-hub session-protocol and agent instruction files.

.claude/rules/repo-boundary.md

@@ -0,0 +1,8 @@
+## Repo boundary
+
+This repo owns **Coordination Engine** only. It does not own:
+
+<!-- TODO: List what belongs in adjacent repos, e.g.:
+- SSH key management → railiance-infra/
+- State hub code     → state-hub/
+-->