create_node/create_edge persisted rows with design_id=null when the
client omitted it (the MCP write tools), so they existed in the DB but
never rendered on the canvas until a container restart reconciled them.
Both routes now fall back to the first design, matching bulk-approve.
Also fix MCP resource reads (homelable://canvas, homelable://edges):
the framework passes a pydantic AnyUrl, not a str, which raised
"'AnyUrl' object has no attribute 'startswith'". Coerce to str.
EdgeResponse now exposes design_id for symmetry with NodeResponse.
ha-relevant: no
Pouzor
cbc2bc03c2