Add hub-core package, docs, and State Hub integration scaffold

Extract the first reusable slice (models, schemas, routers, MCP, migrations)
from state-hub with INTENT/SCOPE, agent instructions, workplan, and aligned
inter_hub capability registry index.

workplans/HUB-WP-0001-statehub-bootstrap.md

@@ -0,0 +1,54 @@
+---
+id: HUB-WP-0001
+type: workplan
+title: "Bootstrap State Hub integration"
+domain: inter_hub
+repo: hub-core
+status: ready
+owner: codex
+topic_slug: inter_hub
+created: "2026-06-16"
+updated: "2026-06-16"
+---
+
+# Bootstrap State Hub integration
+
+**Updated:** 2026-06-16.
+
+## Review Generated Integration Files
+
+```task
+id: HUB-WP-0001-T01
+status: todo
+priority: high
+```
+
+Review `INTENT.md`, `SCOPE.md`, `AGENTS.md`, and `.custodian-brief.md`.
+Replace generated placeholders with repo-specific facts where needed.
+
+## Verify Local Developer Workflow
+
+```task
+id: HUB-WP-0001-T02
+status: todo
+priority: high
+```
+
+Identify the repo's install, test, lint, build, and run commands. Add or refine
+those commands in the agent instructions so future coding sessions can verify
+changes confidently.
+
+## Seed First Real Workplan
+
+```task
+id: HUB-WP-0001-T03
+status: todo
+priority: medium
+```
+
+Create the first implementation workplan for the repository's most important
+next change. After workplan file updates, run from `~/state-hub`:
+
+```bash
+make fix-consistency REPO=hub-core
+```