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.

hub_core/schemas/capability.py

@@ -0,0 +1,99 @@
+import uuid
+from datetime import datetime
+from typing import Any
+
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class CatalogCreate(BaseModel):
+    domain: str
+    capability_type: str
+    title: str
+    description: str | None = None
+    keywords: list[str] = Field(default_factory=list)
+    repo_slug: str | None = None
+
+
+class CatalogPatch(BaseModel):
+    repo_slug: str | None = None
+    description: str | None = None
+    keywords: list[str] | None = None
+    status: str | None = None
+
+
+class CatalogRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    domain_slug: str
+    repo_id: uuid.UUID | None = None
+    repo_slug: str | None = None
+    capability_type: str
+    title: str
+    description: str | None = None
+    keywords: list[str] = Field(default_factory=list)
+    status: str
+    created_at: datetime
+    updated_at: datetime
+
+
+class CapabilityRequestCreate(BaseModel):
+    title: str
+    description: str | None = None
+    capability_type: str
+    priority: str = "medium"
+    requesting_domain: str
+    requesting_agent: str
+    request_context: dict[str, Any] | None = None
+    catalog_entry_id: uuid.UUID | None = None
+
+
+class CapabilityRequestAccept(BaseModel):
+    fulfilling_agent: str
+    fulfillment_context: dict[str, Any] | None = None
+
+
+class CapabilityRequestStatusPatch(BaseModel):
+    status: str
+    note: str | None = None
+
+
+class CapabilityRequestPatch(BaseModel):
+    catalog_entry_id: uuid.UUID | None = None
+    priority: str | None = None
+    request_context: dict[str, Any] | None = None
+    fulfillment_context: dict[str, Any] | None = None
+
+
+class CapabilityRequestDispute(BaseModel):
+    reason: str
+    disputed_by: str
+    suggested_domain: str | None = None
+
+
+class CapabilityRequestRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    title: str
+    description: str | None = None
+    capability_type: str
+    priority: str
+    status: str
+    requesting_domain_slug: str
+    requesting_agent: str
+    request_context: dict[str, Any] | None = None
+    fulfilling_domain_slug: str | None = None
+    fulfilling_agent: str | None = None
+    fulfillment_context: dict[str, Any] | None = None
+    catalog_entry_id: uuid.UUID | None = None
+    resolution_note: str | None = None
+    routing_note: str | None = None
+    dispute_reason: str | None = None
+    disputed_by: str | None = None
+    dispute_suggested_domain: str | None = None
+    disputed_at: datetime | None = None
+    accepted_at: datetime | None = None
+    completed_at: datetime | None = None
+    created_at: datetime
+    updated_at: datetime