fix: scope jest test discovery to project test directory

Jest was discovering and running tests from .claude/worktrees/ alongside
the main test/ directory, causing duplicate fixture inserts against the
same test database and ER_DUP_ENTRY failures.

Author: wa0x6e

jest.config.ts

@@ -4,6 +4,7 @@
  */
 
 export default {
+  roots: ['<rootDir>/test'],
   clearMocks: true,
   collectCoverage: true,
   collectCoverageFrom: ['./src/**'],