Fixed-Point Q15 / Q31 CMSIS-DSP IIR Biquad Quantizer, PostShift & Limit-Cycle Guard

Deterministic Z-plane unit-circle pole-perturbation sensitivity under B-bit quantization + L1-norm internal accumulator overflow scaling & CMSIS-DSP negated-denominator sign convention engine (.c, .h, .json, .csv) built for ARM CMSIS-DSP, STMicroelectronics, Texas Instruments, Microchip dsPIC — zero-upload ephemeral Wasm RAM execution.