Function emit_simd_fadd_f16x4_verilog 

pub fn emit_simd_fadd_f16x4_verilog() -> String

Emit the packed F16×4 add tile: four fp16_add lanes over the 64-bit operands. Module simd_fadd_f16x4 (ports a,b,r). Compile alongside FP16_ADD_V; proven ≡ eval_lanewise_fadd_f16x4 under iverilog.