Create ecs/transaction-database/: transaction-database.ts (extends IndexDatabase, adds
transactions from ./transactions/index.js) plus a transactions/ folder — one mutation per
file + barrel. Type the store param CoreDatabase.Store (entities/resources/archetypes) or
IndexDatabase.Store (reads an index).
Comes after index-database (or core-database if no indexes).
The how is in the auto-loading features/ecs/transactions.md rule.