SHACL-Gated Agent Writes
Concept, MVP scope: one MCP server, two tools, query_graph (SPARQL, read-only) and
propose_fact (writes a candidate triple that must pass SHACL before it lands in the graph).
Every write is validated before commit; there is no path for an agent to bypass the shape.
The goal is deterministic, auditable agent output: an agent can query freely, but it can never assert something the ontology’s shapes reject.