fix: improve sensing accuracy, presence detection, and UI reliability

[KarthikV17]

Server-side fixes (sensing-server)

• Fix ADR-018 packet parsing: correct byte offsets for 20-byte header
  • n_subcarriers: u8 → u16 at bytes [6..7]
  • freq_mhz: u16 → u32 at bytes [8..11]
  • RSSI at byte 16, noise floor at byte 17
• Tune presence detection for faster response:
  • DEBOUNCE_FRAMES: 4 → 2 (faster state transitions)
  • MOTION_EMA_ALPHA: 0.15 → 0.25 (more responsive)
• Add asymmetric person count smoothing:
  • α=0.35 decay when someone leaves (~2-3s response)
  • α=0.20 rise when someone enters (~3-4s response)
  • Prevents false jumps while staying responsive

Firmware fixes (esp32-csi-node)

• Read node_id from NVS config instead of compile-time CONFIG_CSI_NODE_ID
  • Enables unique node IDs per device via provisioning
  • Updated: csi_collector.c, edge_processing.c, wasm_runtime.c, display_ui.c
• Add extern declaration for g_nvs_config in nvs_config.h
• Update provision.py to support both esp32s3 and esp32c6 chips

UI fixes (Observatory)

• Add WebSocket auto-reconnect with exponential backoff:
  • Retries up to 5 times (1s, 2s, 4s, 8s, 16s delays)
  • Shows "RECONNECTING" status with blue pulsing indicator
  • Only falls back to demo mode after all retries exhausted
• Prevents random switches from Live to Demo mode

Tools

• Add csi_inspector.py for packet debugging with correct ADR-018 offsets

[KarthikV17]

@ruvnet please review and let me know if there is any additional testing needed. This has been verified with ESP32-S3.

[ruvnet]

Thanks for the multi-area contribution — there's good intent here but the scope is too broad to land as one PR, and several pieces need verification against current main:

Server-side

• ADR-018 packet offsets — current csi.rs::parse_esp32_frame and the firmware csi_serialize_frame agree on a 20-byte header with n_subcarriers u16 @ [6..7], freq_mhz u32 @ [8..11], rssi i8 @ 16, noise_floor i8 @ 17 — same as your PR claims. If you're seeing offset misalignment on current main, please file an issue with the offending packet hex dump so we can trace the divergence.
• Presence tuning + asymmetric smoothing — these are operator-tunable knobs. Worth its own focused PR with an A/B comparison on the same test fixtures so we can see what the latency-vs-stability tradeoff costs.

Firmware

• node_id from NVS — already in current firmware via fix-marker RuView#232-375-385-386-390 ("defensive early-capture of NVS config before wifi_init_sta() corrupts it"). Please rebase and verify the NVS read is still missing somewhere.
• esp32c6 support in provision.py — overlap with firmware/esp32-csi-node: IDF 6 build, HE CSI config, unicore DSP, provision chip detect #522 / firmware/esp32-hello-world: ESP32-C6 target and ESP-IDF v6 build fixes #524 (krish2718) which just landed ESP-IDF 6 + ESP32-C6 build support including provision.py chip auto-detect. The --chip auto default is now in main.

UI

• WebSocket auto-reconnect — this is genuinely useful and not currently in main. Worth its own focused PR — fix(ui): websocket auto-reconnect with exponential backoff — without the firmware / server changes.

Closing this one as superseded-or-needs-split. Strongest single follow-up: the WebSocket auto-reconnect UX, on its own, against current main. Happy to review that immediately.