Implement semantic link graph persistence for governance control loop

[mdheller]

Context

SocioProphet/sociosphere now contains docs/integrations/hellgraph-semantic-governance-control-loop-v0.md.

HellGraph is designated as the graph-store substrate for the first semantic-governance control loop.

Required v0 capability

Implement or specify a minimal graph persistence/query surface for:

• semantic nodes,
• semantic edges,
• edge provenance,
• graph snapshots,
• receipt references,
• graph diff queries,
• replay lookup by ingestion_run_id, receipt_id, or asset_id.

Mandatory v0 predicates

The graph must support these edge predicates as first-class governed predicates:

• lg:represents
• lg:derivedFrom
• lg:conformsTo
• lg:governedBy
• lg:hasQualitySignal

Acceptance criteria

• A SemanticAsset can be persisted with all five mandatory edges.
• Each edge records edge_id, subject_id, predicate_id, object_id, confidence, assertion_source, observed_at, asserted_at, ingestion_run_id, and provenance_hash.
• A graph snapshot can be associated with a SemanticActivationReceipt.
• Missing required edge classes are externally detectable by SocioSphere admission checks.
• Query path exists for asset lookup by business term, technical profile, policy, quality signal, and receipt id.

Non-goals

• Do not make HellGraph the vocabulary authority; that belongs in ontogenesis.
• Do not mutate clean upstream mirrors for product policy.