feat: ADR-039 edge intelligence — on-device CSI processing pipeline
Implements a dual-core edge processing system for ESP32-S3:
- Lock-free SPSC ring buffer (Core 0 produces, Core 1 consumes)
- Tier 1: phase unwrap, Welford stats, top-K subcarrier selection, delta compression
- Tier 2: presence/motion detection, vital signs (breathing/heart rate via biquad IIR), fall detection
- Vitals UDP packet (magic 0xC5110002, 32 bytes, sent at 1 Hz)
- NVS/Kconfig configurable (edge_tier, thresholds, intervals)
- Backward compatible: tier=0 (default) is a no-op
- GitHub Actions firmware CI: build, binary size gate, credential scan, flash image verification
- Binary: 777 KB (24% free in 1 MB partition)
Co-Authored-By: claude-flow <ruv@ruv.net>
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