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>

firmware/esp32-csi-node/main/nvs_config.h

@@ -39,6 +39,14 @@ typedef struct {
     /* MAC address filter for CSI source selection (Issue #98) */
     uint8_t  filter_mac[6];                   /**< Transmitter MAC to accept (all zeros = no filter). */
     uint8_t  filter_mac_enabled;              /**< 1 = filter active, 0 = accept all. */
+
+    /* ADR-039: Edge intelligence configuration */
+    uint8_t  edge_tier;                       /**< 0=disabled, 1=phase/stats, 2=vitals, 3=reserved. */
+    uint16_t presence_thresh;                 /**< Presence detection threshold (default 50). */
+    uint16_t fall_thresh;                     /**< Fall detection threshold (default 500). */
+    uint16_t vital_window;                    /**< Vital signs window in frames (default 300). */
+    uint16_t vital_interval_ms;               /**< Vitals packet send interval in ms (default 1000). */
+    uint8_t  subk_count;                      /**< Top-K subcarrier count (default 32). */
 } nvs_config_t;
 
 /**