Ensure all doctests pass in libvctrl_handler

[mroczect]

Summary

All code examples inside doc comments (///) must be valid and pass when run as tests. This issue tracks fixing any failing doctests in the handler crate.

Tasks

• Execute cargo test --doc -p libvctrl_handler.
• Investigate every failure and correct the code or the surrounding documentation.
• Common fixes:
  • Add missing use statements.
  • Adjust assertions to match actual behavior.
  • Hide incomplete examples behind ````ignoreorno_run` if they cannot be executed as-is.
• After all fixes, run the doctests again to confirm zero failures.

Acceptance Criteria

• cargo test --doc -p libvctrl_handler returns exit code 0.
• The CI pipeline (if configured) includes a step for doctests.

Dependencies

• Issue 0.2 (documentation must be up‑to‑date before tests can pass).