Use npm ci --ignore-scripts in shared workflows

[fumikito]

Summary

• Replace npm install with npm ci --ignore-scripts in npm.yml, lint.yml
• Prevents execution of postinstall/lifecycle scripts during CI, mitigating supply chain attacks (e.g. axios vulnerability)
• No functional impact: CI doesn't need husky hooks or other lifecycle scripts
• Note: playground-preview-build.yml only exists on the feature/playground-preview branch, so the --ignore-scripts change for that file should be applied there separately

Test plan

• npm.yml: Verify lint/build jobs still pass in consuming plugins
• lint.yml: Verify YAML lint job still passes