Fail closed when simulation invariants cannot be checked

The simulation watcher could report success when invariant queries or checks failed. This change propagates those failures and tests watcher and command lifecycle behavior.

Validation: Simulation watcher and command tests passed locally; the integrated cluster simulation job passed. This topic is also included in draft !5181 (closed). This MR will run its own CI against develop; review and merge coordination should avoid landing the same change twice.