Summary

• Add .neg_fields(), .pre_effects(), .post_effects() batch methods to MatchIR builder
• Migrate all call sites to use batch methods instead of manual loops
• Normalize remaining EffectIR::simple() call to use shorthand methods

Why

Reduces boilerplate when constructing MatchIR instructions. The repeated for eff in effects { m = m.post_effect(eff); } pattern appeared 10+ times across the codebase.