ci: add smoke-test job with artifact upload

[puneeth-grinds]

Summary
Adds a smoke-test job to the CI workflow that runs after the ShellCheck lint job succeeds.

Changes

• Added a test job with needs: lint
• Runs health-check.sh directly on an Ubuntu 24.04 runner
• Captures script output and errors in a timestamped health report
• Uploads the report as a downloadable health-report artifact
• Retains the artifact for 7 days
• Uploads the artifact only when the script completes successfully
• Pinned actions/upload-artifact to a commit SHA

Validation

• Confirmed the test job starts only after lint passes
• Confirmed the health-report artifact appears in the workflow run summary
• Confirmed the artifact is downloadable
• Confirmed a non-zero script exit fails the job and skips artifact upload