Function resolve_entity 

pub async fn resolve_entity(
    gm: &GraphMemory,
    llm: &dyn LlmProvider,
    candidate: &ExtractedEntity,
    session_id: &str,
) -> Result<ResolvedEntity, GraphError>

Run the full dedup pipeline for one extracted entity.

1. Vector search for similar entities
2. If none similar: CREATE directly
3. If similar found: ask LLM for skip/create/merge decision
4. For merge on immutable types: fall back to CREATE