realtime-biquad-dsp

Build a small real-time IIR filter in pure Kotlin from the audio-EQ-cookbook formulas — low-pass, high-pass, or a bank of peaking sections — with cascaded stages for a steeper slope, independent state per channel, neutral stages that keep the state size fixed, and lazy coefficient recompute. Use when a sweepable filter is needed inside an audio callback, when a stereo filter collapses the stereo image, when the…