Add Jest coverage thresholds (soft gate)

[ewilderj]

Description

Configure Jest coverage thresholds to ensure code quality standards are maintained and provide a "soft gate" for future development.

Work Required

1. Update Jest Config: Modify jest.config.js to add coverageThreshold configuration
2. Set Initial Thresholds: Configure reasonable thresholds based on current coverage levels
3. Test Configuration: Verify thresholds work correctly and fail builds appropriately
4. Document Process: Add comments explaining threshold rationale

Implementation Details

Current coverage status (~39% statements according to TODO.md):

• Set initial thresholds that won't break current builds
• Configure global thresholds as a starting point for improvement
• Make thresholds adjustable as coverage improves over time

Proposed Thresholds

coverageThreshold: {
  global: {
    statements: 60,
    branches: 50,
    functions: 55,
    lines: 60
  }
}

Considerations

• Should be achievable with current test improvements in the pipeline
• Can be gradually increased as more tests are added
• Should fail build when thresholds are not met
• Consider per-file thresholds for critical modules later

Files to Modify

• jest.config.js - Add coverageThreshold configuration

Testing

• Run npm test to verify thresholds work
• Temporarily lower thresholds to test failure behavior
• Ensure coverage reports show threshold status

Acceptance Criteria

• Build fails if coverage thresholds are not met
• Thresholds are reasonable for current codebase state
• Configuration is properly documented with rationale
• Coverage reports show threshold status clearly
• Thresholds can be gradually increased as coverage improves