revert: restore memory_entity/memory_edge table names

knowledge_* namespace reserved for future agentic learning tables.
memory_* namespace used for facts, events, and entity graph.

- knowledge_node → memory_entity (reverted)
- knowledge_edge → memory_edge (reverted)
- Old provenance DAG (child_sha/parent_sha) renamed to
  memory_edge_provenance via migration 009
- Kept: runtime queries in versioning.rs, UUID casts, init_schema additions

crates/mem-ingest/src/grm_retriever.rs

@@ -204,7 +204,7 @@ impl GraphContextRetriever for PostgresGrmRetriever {
         debug!("PostgresGrmRetriever: get_entity_context({})", entity_name);
 
         // TODO (Phase 2.5): Implement actual database query
-        // SELECT id, name, summary FROM knowledge_node
+        // SELECT id, name, summary FROM memory_entity
         // WHERE name_embedding <-> query_embedding < (1 - threshold)
         // LIMIT max_entity_context_size
 
@@ -263,7 +263,7 @@ impl GraphContextRetriever for PostgresGrmRetriever {
         debug!("PostgresGrmRetriever: get_fact_context({})", fact_text);
 
         // TODO (Phase 2.5): Implement actual database query
-        // SELECT COUNT(*) FROM knowledge_edge
+        // SELECT COUNT(*) FROM memory_edge
         // WHERE source_id = ? AND target_id = ?
         //   AND fact_embedding <-> query_embedding < (1 - similarity_threshold)
         // AND (t_invalid IS NULL OR t_invalid > NOW())