feat(Syntax/Minimalist): reground so.out consumers on selLinearize

[hawkrobe]

Migrate the remaining Quot.out/so.out planar-representative consumers onto the selection-induced embedding selLinearize .initial (head-initial: head left, complement right), like the Pesetsky caseStackAt and toNonplanar regroundings:

• SmallClause.rightDaughter?, Phase.phaseComplement? — the right daughter is now the genuine complement of the selection-induced order, not an arbitrary representative's
• SpellOut.toLFTree / toPF, ExtendedProjection.computeEPSpine — selection-faithful linearization/spine

All five drop noncomputable (selLinearize is computable). No code consumers (only prose), so no value-dependent theorems shift. Also updates Scope.lean's stale phaseComplement? prose; its dp_phase_barrier_from_pic sorry now needs only the endocentricity link (tok selects b), noted in the TODO.