refactor(Semantics/Events): root-namespace Event, sort via Dynamicity

[hawkrobe]

Consolidates the Event API and adds the neo-Davidsonian argument-introduction substrate the Pylkkänen audit motivated.

• Event moves to the root namespace with its API under namespace Event; Event.sort : Features.Dynamicity replaces the isomorphic EventSort enum (bridge + roundtrip lemmas deleted); EvPred/EventPred inlined to bare Event Time → Prop.
• New Semantics/ArgumentStructure/ArgumentIntroduction.lean (VerbDenot/IntroMode/Event Identification, on the canonical ThematicRel): Pylkkänen's transitivity restriction and "Cause is not a θ-role" are derived from the denotations rather than stipulated.
• Studies/Pylkkanen2008.lean: audit fixes (Table 3.1 section attribution, Finnish causative prediction, Albanian depictives) + §15c/§9 rewired onto the substrate; adds moltmann-2025, hopperdietzel-2024 to references.bib.