Neutral Closure, Weak SU(2)L, and Higgs-Like Branch Locking in ECSM: A Bridge from Triadic Matter Branching to Chiral Weak Coupling

This paper develops a structural bridge between triadic ECSM matter branching and the chiral weak sector. Recent ECSM work proposed that ultraviolet response saturation can localise energy into stable response packets, and that such packets may require triadic internal branch structure: Q_loc → (Q_+, Q_0, Q_-)_loc where Q_+ and Q_- provide polarity or mirror imbalance, while Q_0 provides neutral closure. A subsequent notebook-backed test showed that a neutral closure branch can become dynamically favoured at high response load, after two-branch splitting becomes insufficient. The present paper asks whether this triadic closure structure can provide a route toward weak SU(2)_L coupling. In the Standard Model, left-handed fermions transform as SU(2)_L doublets, while right-handed charged fermions are SU(2)_L singlets. This chiral asymmetry is encoded in the theory, but not mechanically explained at a deeper response level. ECSM proposes a reinterpretation: weak SU(2)_L may describe the effective symmetry of closure-active triadic matter states, while right-handed singlets correspond to branch-locked states that no longer expose the neutral closure channel to weak exchange. In this interpretation, a charged branch and a neutral closure branch form a left-active weak pair: Ψ_L^ECSM = (Q_0, Q_ch)_L Weak interactions are interpreted as local charged-neutral branch conversions inside the unresolved closure sector. The Higgs-like scalar is reinterpreted as an effective medium-locking order parameter: H_SM → Φ_lock(Q, χ) which couples closure-active left states to branch-locked right states and generates inertial mass through excitation-specific response-locking energies: m_f c^2 ↔ E_lock^(f) The paper does not claim to derive the full electroweak theory, the Higgs mass, Yukawa couplings, neutrino oscillations, or the Standard Model gauge group. Its purpose is narrower: to define a structural ECSM bridge from triadic matter branching to chiral weak coupling and Higgs-like mass locking.