feat(adr-018): ESP32-S3 firmware, Rust aggregator, and live CSI pipeline

Complete end-to-end WiFi CSI capture pipeline verified on real hardware:

- ESP32-S3 firmware: WiFi STA + promiscuous mode CSI collection,
  ADR-018 binary serialization, UDP streaming at ~20 Hz
- Rust aggregator CLI binary (clap): receives UDP frames, parses with
  Esp32CsiParser, prints per-frame summary (node, seq, rssi, amp)
- UDP aggregator module with per-node sequence tracking and drop detection
- CsiFrame bridge to detection pipeline (amplitude/phase/SNR conversion)
- Python ESP32 binary parser with UDP reader
- Presence detection confirmed: motion score 10/10 from live CSI variance

Hardware verified: ESP32-S3-DevKitC-1 (CP2102, MAC 3C:0F:02:EC:C2:28),
Docker ESP-IDF v5.2 build, esptool 5.1.0 flash, 20 Rust + 6 Python tests pass.

Co-Authored-By: claude-flow <ruv@ruv.net>

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

@@ -0,0 +1,34 @@
+/**
+ * @file stream_sender.h
+ * @brief UDP stream sender for CSI frames.
+ */
+
+#ifndef STREAM_SENDER_H
+#define STREAM_SENDER_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+/**
+ * Initialize the UDP sender.
+ * Creates a UDP socket targeting the configured aggregator.
+ *
+ * @return 0 on success, -1 on error.
+ */
+int stream_sender_init(void);
+
+/**
+ * Send a serialized CSI frame over UDP.
+ *
+ * @param data Frame data buffer.
+ * @param len  Length of data to send.
+ * @return Number of bytes sent, or -1 on error.
+ */
+int stream_sender_send(const uint8_t *data, size_t len);
+
+/**
+ * Close the UDP sender socket.
+ */
+void stream_sender_deinit(void);
+
+#endif /* STREAM_SENDER_H */