Function materialize_graph_projection 

pub fn materialize_graph_projection(
    source: &Path,
    target: &Path,
    selection: &GraphProjectionSelection,
) -> Result<GraphProjectionSummary, GfError>

Materialize one deterministic graph-only workspace projection.

The target must be absent or empty. Node/edge UUIDs and surrogate IDs are preserved. Every selected edge adds both endpoint nodes; node selection never induces an edge. Topology and property rows are rewritten in UUID order. Only core graph files and required ontology/runtime-catalog metadata are copied; derived indexes and every non-graph domain are excluded.

Errors

Returns validation for missing identities, unsafe/non-empty targets, or malformed graph files, and storage errors for I/O/Arrow/Parquet failures.