This Theorem establishes the complete observable classification of complement-sector feedback. The complement block of admissible form Hcc = aI + bJ (J² = I) produces a Schur correction ΔH = Hᵣc·Hcc⁻¹·Hcr that decomposes into: ΔH = (a/ (a²−b²) ) ·Δ₀ − (b/ (a²−b²) ) ·ΔJ where Δ₀ = Hᵣc·Hcr and ΔJ = Hᵣc·J·Hcr. Five results are established. (I) Scalar invariants protected: the Schur correction lands in spanI, σᵦ, σₓ on the transverse sector and is annihilated by the extraction functional L, μ is invariant under complement-sector feedback. (II) Embedded persistence globally protected: the correction lives in the remainder sector Ωᵣem paired under the mirror involution J; mirror-orbit cancellation (T38) gives λₑff (θ) = 1 independently of local coefficient structure. (III) Propagation orbit structure preserved: feedback deforms transport coefficients but cannot generate new directions in Oq (s), orbit dimension is unchanged. (IV) Spectral deformation real but symmetric: the helicity-twisted component ΔJ is governed by the same spectral discriminant ω = √ (p² − 4a²) as the T30 dressed channel, identifying ΔJ as the operator-level origin of the T30 spectral deformation. This deformation is annihilated before scalar readout by parts (I) and (II), resolving the apparent tension between the nontrivial T30 deformation and the clean T29 extraction. (V) Sole observable manifestation is spectral redistribution across fixed propagation channels, including spectral line splitting, linewidth asymmetry, and beat modulation at frequency p − ω. Two independent protection mechanisms: local null-class annihilation (μ) and global mirror-orbit cancellation (λₑff) operate independently. Status: Null-class protection of μ solid in minimal model, ambient T12/T16 derivation of Schur landing remains open. λₑff = 1 solid, T38 mirror-orbit cancellation operates independently of local structure. Orbit preservation solid via T34–T35. T30 spectral deformation, real and symmetric solid. Spectral redistribution as sole observable structural — not yet derived from full ambient architecture. Two independent protection mechanisms solid. Dependencies: T26, T29, T30, T34, T35, T37, T38.
Craig Edwin Holdway (Sun,) studied this question.