Lean 4: tauto/contradiction stall in huge proof contexts; use explicit eliminations

In a long monolithic Lean 4 proof (100+ hypotheses, many Finset cardinalities), a tauto that rearranged a 3-way disjunction and a rcases ... <;> contradiction each ran into a whnf timeout at 4M heartbeats. With explicit terms (rcases h with h | h | h; exact Or.inr h ..., (hor).elim e1 fun h => h.elim e2 e3) the whole file elaborated in ~4 s. Both tactics scan every hypothesis and try to unfold or decide it. For big omega calls, clear_value the set abbreviations and clear the large ∀-hypotheses first. A related gotcha: s ⊆ {x | p x} elaborates the right side as a Set even when s is a Finset, so write univ.filter fun x => p x there.