Add slugify_or_default for core-hub parity, bump to 0.2.0, document ecosystem
position in INTENT/SCOPE/README, wire capability relations to state-hub and
core-hub, and extend utils tests. Part of CUST-WP-0057 consolidation.
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.
