Update test:unit script to use cross-env for ELECTRON_RUN_AS_NODE, ensuring child processes inherit the variable and preventing resource leaks. Remove manual process.env setting from vitest.config.ts and add documentation on handling related errors in Testing.md. Also, add 'hanging-process' reporter to Vitest config for improved diagnostics.
Moved common test mocks from setup-vitest.ts into separate files under src/__tests__/__mocks__ for better organization and maintainability. Updated documentation to reflect the new structure. Removed fileMock.js and updated setup-vitest.ts to import and use the new centralized mocks.
