Fix linux-sysmonitor compatibility issues inside Docker container

[puneeth-grinds]

What

Create the first GitHub Actions workflow that runs ShellCheck on health-check.sh on every push and pull request.

Tasks

• Create .github/workflows/ci.yml
• Set trigger: on: [push, pull_request]
• Add job lint with runs-on: ubuntu-latest
• Checkout repo with actions/checkout@v4 (pin to commit SHA, add version in comment)
• Install shellcheck via apt
• Run shellcheck scripts/health-check.sh

Acceptance Criteria

• Workflow triggers on every push to any branch
• Introducing a syntax error in health-check.sh fails the workflow
• Action is pinned to a commit SHA, not @v4

Commit

ci: add ShellCheck lint workflow