feat(M12.2): add electroweak lepton and neutrino phenomenology

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M12.2

Extends M12.1 with executable tree-level electroweak, charged-lepton, and neutrino phenomenology discovered through the full Lean/ZIL particle-module audit.

Electroweak sector

• constructs the neutral (W3,B) mass matrix;
• verifies one massless photon eigenvalue and the generated Z eigenvalue;
• checks m_W = m_Z cos(theta_W) and tree-level rho = 1;
• checks the equivalent electric-charge forms e = g sin(theta_W) = g' cos(theta_W);
• evaluates the supplied tree-level QED, four-Fermi neutrino, W-width and Z-width carriers.

Lepton and neutrino sector

• records the supplied electron, muon and tau mass/lifetime data without promoting them to predictions;
• verifies mass ordering, tau branching normalization and the Sargent m^5 width ratio;
• checks Michel and tau-decay family-number rules;
• reconstructs a normal-order neutrino mass spectrum from supplied splittings;
• constructs the supplied PMNS matrix, verifies unitarity and checks normalized vacuum-oscillation probabilities.

Formal and ZIL authority

Pins:

• ElectroweakGaugeBosonPhenomenology.electroweakGaugeBosonPhenomenology_checked;
• LeptonFlavorNumbers.sargent_universality_ratio;
• MichelDecayFlavor.michel_decay_complete;
• NeutrinoModel.deltaM21Sq_pos_of_normal.

The ZIL graph explicitly excludes predicted PMNS angles, numerical gauge-boson masses, radiative corrections, and a computed Michel spectrum.

Validation

Locally validated before publication:

• M12 package compilation passed;
• all current M12 formal ledgers parsed;
• M12.1 and M12.2 focused tests passed.

No repository CI workflow was added or modified.

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Superseded by PR #159. The complete M12.2 electroweak/lepton/neutrino changes were preserved exactly and combined with M12.3 into one commit directly on the merged M12.1 main head.