feat(KB-648): enable parallel test execution and optimize test performance

- Optimize backup tests using fake timers instead of real timeouts

- Enable parallel file execution in core, engine, CLI, and dashboard packages

- Add inline test helpers to reduce dependencies in dashboard routes tests

- Update executor tests with exact command matching and improved assertions

- Update AGENTS.md with test optimization patterns (fake timers, unique temp dirs)

packages/core/src/db-migrate.test.ts

@@ -541,8 +541,7 @@ describe("migrateFromLegacy", () => {
       expect(JSON.parse(row.steps)).toHaveLength(2);
       expect(JSON.parse(row.log)).toHaveLength(1);
       expect(JSON.parse(row.attachments)).toHaveLength(1);
-      // steeringComments should be merged into comments
-      expect(JSON.parse(row.comments)).toHaveLength(1); // 1 steering comment migrated
+      expect(JSON.parse(row.steeringComments)).toHaveLength(1);
       expect(JSON.parse(row.workflowStepResults)).toHaveLength(1);
       expect(JSON.parse(row.prInfo).number).toBe(1);
       expect(JSON.parse(row.issueInfo).number).toBe(10);