Interior Observer Paper 11: Stress-Testing the Framework — Perturbation Theory, Curvature Decoherence, and the Species-Dependent Modular Projection

Paper 11 subjects the Interior Observer (IO) cosmological framework to a comprehensive stress test against CMB perturbation theory, BAO absolute distances, and Big Bang nucleosynthesis. The framework entered with six existential observational failures (θ* at 48σ, R at 18σ, ℓ₁ off by 18%, H₀ off by 16%, r_s at 50σ, BAO χ² = 385). Through 26 rounds of computation verified by independent AI systems, the paper derives a Schur complement curvature formula, identifies a species-dependent baryon correction, and proposes a Non-Conformal Modular Principle unifying baryon loading and recombination through a shared modular exponent. The resulting cosmology achieves θ* within 0.035% of Planck and R within 0.2σ at zero free parameters. A CLASS Boltzmann computation establishes a boundary/bulk observable-class split: CMB angular observables use the projected baryon correction while BBN and BAO use the geometric density. Remaining tensions include D/H at 38% high and a BAO distance residual (χ² = 42.8). Part of an 11-paper series deriving cosmological observables from the single input M_U = 4.50 × 10⁵³ kg with zero free parameters. v1.2 correction (Paper 12, DOI: 10.5281/zenodo.18936508): Baryon sector annotations per Paper 12 (Baryon Dictionary Principle). Paper 12 derived f_b = 2γ/x = 0.313, superseding f_b = 0.25. A γ-scan proved the baryon correction is rational (F = ⟨K⟩x/(8γ) = 1.381, RMS 1.4%) rather than exponential (F = exp(K_geom/(2⟨K⟩)) = 1.623, RMS 48.9%). The exponential derivation in §2.2/§5 is retained as research history; annotations mark where it is superseded. The Non-Conformal Modular Principle proposed in §5 is superseded by the rational form. D/H crisis resolved (2.49 × 10⁻⁵, −1.2σ). Master table baryon entries annotated with BDP values. The Schur complement curvature formula, N_eff = Δ, θ* and R results, boundary/bulk split, and BAO methodology are all unaffected.