US-10 Expanded Automated Testing Infrastructure

[TheCelestial25]

• User Story: As a Project Maintainer, I want a comprehensive testing suite tracking individual React components, utility files, and round-trip parsing, so that future updates don't accidentally introduce regressions.
• Priority: P1
• Phase: Phase 3: Weeks 4–5
• Acceptance Criteria:
  • Set up component unit tests using Jest/Vitest and React Testing Library for baseline layout elements (such as the Header and GraphToolbar).
  • Write unit tests for round-trip parsing utilities to verify that raw CTO text maps to the visual model and back cleanly without data loss.
  • Target a minimum baseline of 80% test coverage across the helper engines located inside src/utils/.