Three root causes identified for 4-5 clicks/sec in live audio streaming:

1. Buffer bloat in captureSpectrum (PRIMARY)
 allIQ reads drained the entire SDR buffer (196k-1M+ samples), causing
 extraction times to vary wildly. Large frames took >150ms to process,
 starving the next frame and creating a positive feedback loop.
 feed_gap warnings (152-218ms) directly correlated with audible clicks.

 Fix: cap allIQ to 2 frame intervals (~682k samples) after reading.
 Full buffer is still drained and ingested into the ring buffer;
 only the extraction/streaming path is capped.

2. Stateless decimation in processSnippet
 dsp.Decimate() restarted at index 0 every frame. When snippet length
 was not divisible by the decimation factor (e.g. 512kHz/3=170.6kHz,
 snippet % 3 != 0), a sample timing discontinuity occurred at each
 frame boundary.

 Fix: new dsp.DecimateStateful() preserves the decimation phase index
 across calls. Session field preDemodDecimPhase added to streamSession
 with proper snapshot/restore for segment splits.

3. Resampler bandwidth too narrow (10.8kHz instead of 15kHz)
 Polyphase resampler prototype cutoff fc=0.45/max(L,M) limited audio
 to 10.8kHz, cutting off FM stereo content above that.

 Fix: increase fc to 0.90/max(L,M), passing up to 22.8kHz.
 Kaiser window (β=6) maintains -60dB sidelobe suppression.

Files changed:
 cmd/sdrd/pipeline_runtime.go - allIQ cap after buffer read
 internal/dsp/fir.go - DecimateStateful()
 internal/dsp/decimate_test.go - 5 tests for stateful decimation
 internal/dsp/resample.go - fc 0.45 → 0.90
 internal/recorder/streamer.go - preDemodDecimPhase field + usage