Improve error formatting in tests

- Replace [object Object] errors with readable messages by using robust error formatting across test suites
- Introduce formatTestError helper and apply it in all catch blocks and error throws
- Update approvalPipelineTests and related suites to utilize improved error extraction for better debugging

src/lib/integrationTests/index.ts

@@ -7,5 +7,6 @@
 export { IntegrationTestRunner } from './testRunner';
 export { allTestSuites } from './suites';
 export { formatResultsAsMarkdown, formatSingleTestAsMarkdown } from './formatters';
+export { formatTestError } from './formatTestError';
 
 export type { TestResult, Test, TestSuite } from './testRunner';