FW-H2 Jordan–Hölder Lemma

Formally answers the "Additive FW-H2 compiler" problem listed as the first priority in Document 34. Let $V=E[p]|_{G_{\mathbf Q_p}}$, $\omega=\bar\chi_{\rm cyc}$; if $V$ is reducible, write $V^{ss}=\lambda\oplus\mu$, and from the Weil pairing we get $\lambda\mu=\omega$. The local forbidden form of Fouquet–Wan Theorem 1.7 is $\chi\oplus\omega\chi$. The core lemma precisely proves: $V^{ss}\simeq\chi\oplus\omega\chi$ (for some $\chi$) if and only if $\lambda^2=1$ or $\mu^2=1$—the proof utilizes determinant comparison ($\omega=\omega\chi^2\Rightarrow\chi^2=1$) and reverse construction ($\lambda^2=1\Rightarrow\mu=\omega\lambda^{-1}=\omega\lambda$) in both directions, symmetrically handling the $\mu^2=1$ case. The conclusion is boxed: $\mathrm{FW17\text{-}H2\ FAIL}\iff$ some Jordan–Hölder character is quadratic or trivial. The document finally adds a sentence directly echoing a key fact from all previous branches: if $V$ is irreducible over $\mathbf F_p$, it cannot be a character direct sum, hence H2 automatically PASSes—this is exactly the mathematical reason why the good supersingular branch could get H2 for free from the very beginning, which is now formally proven rather than just cited.