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-cli/src/metrics.rs

@@ -274,9 +274,9 @@ pub static WRITE_BYTES_TOTAL: Counter = Counter::new(
     "memory_write_bytes_total", "Total bytes written to storage");
 
 pub static DB_ENTITY_COUNT: Gauge = Gauge::new(
-    "memory_db_entity_count", "Current entity count in knowledge_node table");
+    "memory_db_entity_count", "Current entity count in memory_entity table");
 pub static DB_EDGE_COUNT: Gauge = Gauge::new(
-    "memory_db_edge_count", "Current edge count in knowledge_edge table");
+    "memory_db_edge_count", "Current edge count in memory_edge table");
 pub static DB_CHUNK_COUNT: Gauge = Gauge::new(
     "memory_db_chunk_count", "Current chunk count in memory_chunks table");
 
@@ -436,9 +436,9 @@ pub static DB_TRANSACTION_DURATION: Lazy<Histogram> = Lazy::new(||
 
 // Table-specific row counts (updated periodically)
 pub static DB_TABLE_ENTITY_ROWS: Gauge = Gauge::new(
-    "memory_db_table_entity_rows", "Rows in knowledge_node table");
+    "memory_db_table_entity_rows", "Rows in memory_entity table");
 pub static DB_TABLE_EDGE_ROWS: Gauge = Gauge::new(
-    "memory_db_table_edge_rows", "Rows in knowledge_edge table");
+    "memory_db_table_edge_rows", "Rows in memory_edge table");
 pub static DB_TABLE_CHUNK_ROWS: Gauge = Gauge::new(
     "memory_db_table_chunk_rows", "Rows in memory_chunks table");