Document CLI warning behavior and output verbosity controls

[dangrondahl]

Problem

There is no documentation explaining:

1. What [warning] messages the CLI can emit and what they mean
2. That warnings are written to stderr and do not affect exit codes
3. That there is currently no way to suppress warnings (no --quiet flag, no log-level config)
4. How to handle warnings in CI/CD pipelines

Context

User raised this concern — their pipeline users see CLI warnings and worry they indicate real problems.

CI environments make this worse: In Jenkins, Azure DevOps, Bitbucket Pipelines, and GitHub Actions, stdout and stderr are multiplexed into a single build log. Users cannot distinguish warning lines from normal output. Some CI systems render stderr with error-level formatting (red text), making non-fatal warnings look like failures. Redirecting stderr (2>/dev/null) is not a practical workaround because it also suppresses genuine error messages.

The --debug flag is documented (client_reference/kosli.md, troubleshooting/subshell_stderr.md) but the inverse (reducing output) is not addressed.

Suggested scope

• Add a section to the CLI reference or troubleshooting docs explaining warning behavior: what triggers them, that they're non-fatal, and that they appear in stderr
• Explain the CI multiplexing issue and why warnings appear alongside normal output in build logs
• Document any available workarounds (with caveats)
• Cross-reference with --debug documentation
• If/when a --quiet flag is added to the CLI, document it here