ci: add unit test workflow with coverage thresholds and lint fixes

[sugat009]

Summary

• Add GitHub Actions CI workflow (unit_tests.yml) that runs build, lint, and test with coverage on every PR to main
• Add .nycrc.json with coverage thresholds: 95% statements/lines/functions, 85% branches
• Align ESLint config with CHT standards by adding eslint-plugin-n (Node.js rules), eslint-plugin-promise, and eslint-plugin-no-only-tests
• Fix all pre-existing lint errors: exclude coverage/ from ESLint, allow require() in tests (proxyquire), resolve no-explicit-any warnings
• Update @typescript-eslint/eslint-plugin and @typescript-eslint/parser to latest v8 (8.58.2)

Test plan

• CI workflow triggers on PR and passes build, lint, and test steps
• Coverage thresholds enforce minimums (95%/85% branches)
• no-only-tests rule catches accidental it.only() / describe.only() in tests
• npm run lint passes locally with 0 errors and 0 warnings
• Existing PRs work after rebasing on main

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Hareet]

LGTM!

Summary

● Confirmed: no-only-tests rule is correctly wired — fired with describe.only not permitted error. File reverted, no diff. Test plan scenario passes.

Coverage vs thresholds (.nycrc.json):

  ┌────────────┬────────┬───────────┐                                                                                                                                                                                          
  │   Metric   │ Result │ Threshold │                                                                                
  ├────────────┼────────┼───────────┤                                                                                                                                                                                          
  │ Statements │ 96.82% │ 95 ✓      │
  ├────────────┼────────┼───────────┤                                                                                                                                                                                          
  │ Branches   │ 86.13% │ 85 ✓      │                                                                                
  ├────────────┼────────┼───────────┤
  │ Functions  │ 100%   │ 95 ✓      │
  ├────────────┼────────┼───────────┤
  │ Lines      │ 96.77% │ 95 ✓      │
  └────────────┴────────┴───────────┘