Test Build Analysis handling with Arcade CI mode

[svick]

This draft PR runs a temporary deterministic failure to validate the proposed fix for #7344.

Experiment sequence

1. Capture a failing CI build without a matching KBE.
2. Create a temporary KBE from that build.
3. Confirm Build Analysis remains red because the Helix wrapper also reports a generic exit-code-1 error.
4. Enable Arcade CI mode for the Helix invocation and confirm Build Analysis becomes green with the same test failure matched by the KBE.
5. Remove the temporary failing test before this PR is ready for review.

The marker MLNET_BUILD_ANALYSIS_CI_MODE_EXPERIMENT_7344 is intentionally unique and temporary.