Function validate_program_graph 

pub fn validate_program_graph(
    shape: ProgramGraphShape,
    nodes: &[u32],
    edge_offsets: &[u32],
    edge_targets: &[u32],
    edge_kind_mask: &[u32],
    node_tags: &[u32],
) -> Result<(), GraphValidationError>

Validate an in-memory ProgramGraph against the wire invariants.

Called by conformance harnesses on synthetic fixtures and by downstream graph pipelines on freshly-emitted graphs before dispatch. The backend dispatcher rejects any graph whose CSR breaks these invariants.