feat: cross-node fusion + DynamicMinCut + RSSI tracking (v0.5.3)

* feat(server): cross-node RSSI-weighted feature fusion + benchmarks

Adds fuse_multi_node_features() that combines CSI features across all
active ESP32 nodes using RSSI-based weighting (closer node = higher weight).

Benchmark results (2 ESP32 nodes, 30s, ~1500 frames):

  Metric               | Baseline | Fusion  | Improvement
  ---------------------|----------|---------|------------
  Variance mean        |    109.4 |    77.6 | -29% noise
  Variance std         |    154.1 |   105.4 | -32% stability
  Confidence           |    0.643 |   0.686 | +7%
  Keypoint spread std  |      4.5 |     1.3 | -72% jitter
  Presence ratio       |   93.4%  |  94.6%  | +1.3pp

Person count still fluctuates near threshold — tracked as known issue.

Verified on real hardware: COM6 (node 1) + COM9 (node 2) on ruv.net.

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

* fix(ui): add client-side lerp smoothing to pose renderer

Keypoints now interpolate between frames (alpha=0.25) instead of
jumping directly to new positions. This eliminates visual jitter
that persists even with server-side EMA smoothing, because the
renderer was drawing every WebSocket frame at full rate.

Applied to skeleton, keypoints, and dense body rendering paths.

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

* feat: DynamicMinCut person separation + UI lerp smoothing

- Added ruvector-mincut dependency to sensing server
- Replaced variance-based person scoring with actual graph min-cut on
  subcarrier temporal correlation matrix (Pearson correlation edges,
  DynamicMinCut exact max-flow)
- Recalibrated feature scaling for real ESP32 data ranges
- UI: client-side lerp interpolation (alpha=0.25) on keypoint positions
- Dampened procedural animation (noise, stride, extremity jitter)
- Person count thresholds retuned for mincut ratio

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

* docs: update CHANGELOG with v0.5.1-v0.5.3 releases

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

firmware/esp32-csi-node/sdkconfig.defaults.8mb_backup

@@ -0,0 +1,33 @@
+# ESP32-S3 CSI Node — Default SDK Configuration
+# This file is applied automatically by idf.py when no sdkconfig exists.
+
+# Target: ESP32-S3
+CONFIG_IDF_TARGET="esp32s3"
+
+# Use custom partition table (8MB flash with OTA — ADR-045)
+CONFIG_PARTITION_TABLE_CUSTOM=y
+CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions_display.csv"
+
+# Flash configuration: 8MB (Quad SPI)
+CONFIG_ESPTOOLPY_FLASHSIZE_8MB=y
+CONFIG_ESPTOOLPY_FLASHSIZE="8MB"
+
+# Compiler optimization: optimize for size to reduce binary
+CONFIG_COMPILER_OPTIMIZATION_SIZE=y
+
+# Enable CSI (Channel State Information) in WiFi driver
+CONFIG_ESP_WIFI_CSI_ENABLED=y
+
+# NVS encryption disabled by default (requires eFuse provisioning).
+# Enable only after burning HMAC key to eFuse block.
+# CONFIG_NVS_ENCRYPTION is not set
+
+# Disable unused features to reduce binary size
+CONFIG_BOOTLOADER_LOG_LEVEL_WARN=y
+CONFIG_LOG_DEFAULT_LEVEL_INFO=y
+
+# LWIP: enable extended socket options for UDP multicast
+CONFIG_LWIP_SO_RCVBUF=y
+
+# FreeRTOS: increase task stack for CSI processing
+CONFIG_ESP_MAIN_TASK_STACK_SIZE=8192