Add health metrics tab coverage

[Mayreck]

Summary

• Add accessible tab semantics to the Health Metrics chart switcher
• Add keyboard navigation with ArrowLeft, ArrowRight, Home, and End
• Add Vitest/RTL coverage that mocks child charts and verifies data routing for all four tabs
• Document the coverage in docs/testing/HEALTH_METRICS_TABS_TESTS.md

Validation

• npx vitest run src/components/dashboard/CommitmentHealthMetrics.test.tsx
• npx eslint src/components/dashboard/CommitmentHealthMetrics.tsx src/components/dashboard/CommitmentHealthMetrics.test.tsx

Baseline notes

• Existing repo-wide npm run lint and npx tsc --noEmit remain blocked by unrelated baseline syntax/lint issues noted in PR Add RecentAttestationsPanel test coverage #663, including src/app/api/commitments/[id]/settle/route.ts and src/components/modals/CommitmentDetailsModal.tsx.

Closes #646.

[vercel]

@Mayreck is attempting to deploy a commit to the 1nonly's projects Team on Vercel.

A member of the Team first needs to authorize it.

[GBOYEE]

I'd like to work on this.

Approach:

• I'll write the test cases and ensure they pass with full coverage
• Verify with existing tests + add new ones if needed

Estimated effort: ~1-2 hours. PR incoming shortly.

[GBOYEE]

I'd like to work on this.

Approach:

• I'll write the test cases and ensure they pass with full coverage
• Verify with existing tests + add new ones if needed

Estimated effort: ~1-2 hours. PR incoming shortly.