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

tests/it_phase7_gate.rs

@@ -50,8 +50,8 @@ async fn test_phase7_composition_gate() {
 
 // T7.1: Schema Checks
 fn assert_tables_exist() {
-    // Verify knowledge_node_version table
-    // Verify knowledge_edge_version table
+    // Verify memory_entity_version table
+    // Verify memory_edge_version table
     // Verify index coverage
 }
 
@@ -107,7 +107,7 @@ async fn test_edge_diff_endpoint() {
 async fn test_audit_logger_log_entity() {
     // Create entity snapshot
     // Call audit_logger.log_entity()
-    // Verify record inserted in knowledge_node_version
+    // Verify record inserted in memory_entity_version
     // Verify changed_by populated from JWT sub
     // Verify fields_changed array computed
 }
@@ -120,9 +120,9 @@ async fn test_audit_logger_history() {
 }
 
 async fn test_audit_logger_immutability() {
-    // Try to UPDATE knowledge_node_version
+    // Try to UPDATE memory_entity_version
     // Should fail (trigger fires)
-    // Try to DELETE knowledge_node_version
+    // Try to DELETE memory_entity_version
     // Should fail (trigger fires)
     // Verify log is append-only
 }