[Critical] Add test coverage metrics and CI gates

[jessfortemnaturae8717]

Problem

No test coverage metrics despite having 689 tests. Can't verify quality or catch coverage regressions.

Current state:

• @vitest/coverage-v8 installed as devDependency
• No coverage configuration in vitest.config.ts
• No coverage reports generated
• No CI gates for coverage thresholds

Risk

• New code may lack tests
• Coverage could regress without notice
• Can't demonstrate quality to enterprise customers

Solution

Enable coverage reporting with minimum thresholds.

// vitest.config.ts
export default defineConfig({
  test: {
    coverage: {
      provider: 'v8',
      reporter: ['text', 'json', 'html'],
      exclude: ['node_modules', 'dist', '**/*.test.ts'],
      thresholds: {
        statements: 80,
        branches: 75,
        functions: 80,
        lines: 80,
      },
    },
  },
});

Tasks

• Configure vitest coverage in vitest.config.ts
• Add npm run test:coverage script
• Generate baseline coverage report
• Add coverage badge to README
• Add CI job to check coverage thresholds
• Fail PR if coverage drops below threshold
• Upload coverage to Codecov/Coveralls

Proposed Thresholds

Metric	Minimum	Target
Statements	80%	90%
Branches	75%	85%
Functions	80%	90%
Lines	80%	90%

Acceptance Criteria

• npm run test:coverage generates HTML report
• CI fails if coverage below thresholds
• Coverage badge visible in README
• Coverage trend visible in PR comments

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Priority: P1 — Required for enterprise credibility