This work presents Eormen, a deterministic, non-interfering observational system designed to evaluate structural sensitivity in complex dynamical traces under strict architectural constraints. Eormen separates frozen reality generation from observer replay, ensuring that observational channels cannot alter the underlying generative process. This architectural separation enables explicit determinism, non-interference verification, and reproducible replay under fixed runtime and coefficient artefacts. The study proceeds in two stages. First, integrity is established at scale using publicly available NASA C-MAPSS datasets. Across 609 completed runs spanning FD002, FD003, and FD004 subsets, strict theorem-gated execution passed without failure, demonstrating deterministic stability and non-interference under locked configuration. Second, an observational sensitivity phase (v2-OBS) evaluates system response to structured, theorem-legal perturbations. An initial pre-excitation phase demonstrated suppressed observer response despite measurable reality perturbation. A subsequent theorem-preserving, one-way observer excitation mechanism restored non-trivial observer dynamics without introducing feedback into the generative trace. Dual acceptance regimes are explicitly retained: v1 (legacy monotone calibration criterion): not satisfied. v2 (control-to-high sensitivity criterion): satisfied and designated as the primary acceptance regime for this phase. The work establishes reproducible observational sensitivity under deterministic and non-interfering constraints. It does not claim monotone calibration, predictive performance, remaining useful life estimation, optimisation capability, or policy recommendation. All results are traceable to fixed artefact roots and recorded provenance metadata.