Module engine 

Catalog storage engine.

This is the narrow bridge between relational concepts and the generic lower layers.

SQL / planner / executor
         |
         v
     CatalogEngine
         |
  +------+------+
  |             |
rows/indexes  schema metadata
  |             |
  +-------> generic B-tree
                   |
                   v
                 pager

Responsibilities:

• hold runtime metadata such as row counts and next rowid;
• persist schema roots and table metadata;
• expose relational operations in terms of rows, keys, and cursors;
• prevent page- and node-level details from leaking into query/catalog code.

This file should coordinate access methods, not define relational byte formats. Row codecs and index-key codecs live beside the catalog model so the generic lower layers remain reusable.

Structs

CatalogEngine

CatalogEngineSnapshot

CatalogIntegrityReport

CatalogStorageStats

TableRuntimeMetadata