feat(server): per-node state pipeline for multi-node sensing (#249)

README.md

@@ -1,7 +1,7 @@
 # π RuView
 
 <p align="center">
-  <a href="https://ruvnet.github.io/RuView/">
+  <a href="https://x.com/rUv/status/2037556932802761004">
     <img src="assets/ruview-small-gemini.jpg" alt="RuView - WiFi DensePose" width="100%">
   </a>
 </p>

docs/adr/ADR-068-per-node-state-pipeline.md

@@ -0,0 +1,182 @@
+# ADR-068: Per-Node State Pipeline for Multi-Node Sensing
+
+| Field      | Value                               |
+|------------|-------------------------------------|
+| Status     | Accepted                            |
+| Date       | 2026-03-27                          |
+| Authors    | rUv, claude-flow                    |
+| Drivers    | #249, #237, #276, #282              |
+| Supersedes | —                                   |
+
+## Context
+
+The sensing server (`wifi-densepose-sensing-server`) was originally designed for
+single-node operation. When multiple ESP32 nodes send CSI frames simultaneously,
+all data is mixed into a single shared pipeline:
+
+- **One** `frame_history` VecDeque for all nodes
+- **One** `smoothed_person_score` / `smoothed_motion` / vital sign buffers
+- **One** baseline and debounce state
+
+This means the classification, person count, and vital signs reported to the UI
+are an uncontrolled aggregate of all nodes' data. The result: the detection
+window shows identical output regardless of how many nodes are deployed, where
+people stand, or how many people are in the room (#249 — 24 comments, the most
+reported issue).
+
+### Root Cause Verified
+
+Investigation of `AppStateInner` (main.rs lines 279-367) confirmed:
+
+| Shared field              | Impact                                     |
+|---------------------------|--------------------------------------------|
+| `frame_history`           | Temporal analysis mixes all nodes' CSI data |
+| `smoothed_person_score`   | Person count aggregates all nodes           |
+| `smoothed_motion`         | Motion classification undifferentiated      |
+| `smoothed_hr` / `br`     | Vital signs are global, not per-node        |
+| `baseline_motion`         | Adaptive baseline learned from mixed data   |
+| `debounce_counter`        | All nodes share debounce state              |
+
+## Decision
+
+Introduce **per-node state tracking** via a `HashMap<u8, NodeState>` in
+`AppStateInner`. Each ESP32 node (identified by its `node_id` byte) gets an
+independent sensing pipeline with its own temporal history, smoothing buffers,
+baseline, and classification state.
+
+### Architecture
+
+```
+                     ┌─────────────────────────────────────────┐
+   UDP frames        │           AppStateInner                  │
+   ───────────►      │                                         │
+   node_id=1    ──►  │  node_states: HashMap<u8, NodeState>    │
+   node_id=2    ──►  │    ├── 1: NodeState { frame_history,    │
+   node_id=3    ──►  │    │      smoothed_motion, vitals, ... }│
+                     │    ├── 2: NodeState { ... }              │
+                     │    └── 3: NodeState { ... }              │
+                     │                                         │
+                     │  ┌── Per-Node Pipeline ──┐               │
+                     │  │ extract_features()     │               │
+                     │  │ smooth_and_classify()  │               │
+                     │  │ smooth_vitals()        │               │
+                     │  │ score_to_person_count()│               │
+                     │  └────────────────────────┘               │
+                     │                                         │
+                     │  ┌── Multi-Node Fusion ──┐               │
+                     │  │ Aggregate person count │               │
+                     │  │ Per-node classification│               │
+                     │  │ All-nodes WebSocket msg│               │
+                     │  └────────────────────────┘               │
+                     │                                         │
+                     │  ──► WebSocket broadcast (sensing_update) │
+                     └─────────────────────────────────────────┘
+```
+
+### NodeState Struct
+
+```rust
+struct NodeState {
+    frame_history: VecDeque<Vec<f64>>,
+    smoothed_person_score: f64,
+    prev_person_count: usize,
+    smoothed_motion: f64,
+    current_motion_level: String,
+    debounce_counter: u32,
+    debounce_candidate: String,
+    baseline_motion: f64,
+    baseline_frames: u64,
+    smoothed_hr: f64,
+    smoothed_br: f64,
+    smoothed_hr_conf: f64,
+    smoothed_br_conf: f64,
+    hr_buffer: VecDeque<f64>,
+    br_buffer: VecDeque<f64>,
+    rssi_history: VecDeque<f64>,
+    vital_detector: VitalSignDetector,
+    latest_vitals: VitalSigns,
+    last_frame_time: Option<std::time::Instant>,
+    edge_vitals: Option<Esp32VitalsPacket>,
+}
+```
+
+### Multi-Node Aggregation
+
+- **Person count**: Sum of per-node `prev_person_count` for active nodes
+  (seen within last 10 seconds).
+- **Classification**: Per-node classification included in `SensingUpdate.nodes`.
+- **Vital signs**: Per-node vital signs; UI can render per-node or aggregate.
+- **Signal field**: Generated from the most-recently-updated node's features.
+- **Stale nodes**: Nodes with no frame for >10 seconds are excluded from
+  aggregation and marked offline (consistent with PR #300).
+
+### Backward Compatibility
+
+- The simulated data path (`simulated_data_task`) continues using global state.
+- Single-node deployments behave identically (HashMap has one entry).
+- The WebSocket message format (`sensing_update`) remains the same but the
+  `nodes` array now contains all active nodes, and `estimated_persons` reflects
+  the cross-node aggregate.
+- The edge vitals path (#323 fix) also uses per-node state.
+
+## Scaling Characteristics
+
+| Nodes | Per-Node Memory | Total Overhead | Notes |
+|-------|----------------|----------------|-------|
+| 1     | ~50 KB         | ~50 KB         | Identical to current |
+| 3     | ~50 KB         | ~150 KB        | Typical home setup |
+| 10    | ~50 KB         | ~500 KB        | Small office |
+| 50    | ~50 KB         | ~2.5 MB        | Building floor |
+| 100   | ~50 KB         | ~5 MB          | Large deployment |
+| 256   | ~50 KB         | ~12.8 MB       | Max (u8 node_id) |
+
+Memory is dominated by `frame_history` (100 frames x ~500 bytes each = ~50 KB
+per node). This scales linearly and fits comfortably in server memory even at
+256 nodes.
+
+## QEMU Validation
+
+The existing QEMU swarm infrastructure (ADR-062, `scripts/qemu_swarm.py`)
+supports multi-node simulation with configurable topologies:
+
+- `star`: Central coordinator + sensor nodes
+- `mesh`: Fully connected peer network
+- `line`: Sequential chain
+- `ring`: Circular topology
+
+Each QEMU instance runs with a unique `node_id` via NVS provisioning. The
+swarm health validator (`scripts/swarm_health.py`) checks per-node UART output.
+
+Validation plan:
+1. QEMU swarm with 3-5 nodes in mesh topology
+2. Verify server produces distinct per-node classifications
+3. Verify aggregate person count reflects multi-node contributions
+4. Verify stale-node eviction after timeout
+
+## Consequences
+
+### Positive
+- Each node's CSI data is processed independently — no cross-contamination
+- Person count scales with the number of deployed nodes
+- Vital signs are per-node, enabling room-level health monitoring
+- Foundation for spatial localization (per-node positions + triangulation)
+- Scales to 256 nodes with <13 MB memory overhead
+
+### Negative
+- Slightly more memory per node (~50 KB each)
+- `smooth_and_classify_node` function duplicates some logic from global version
+- Per-node `VitalSignDetector` instances add CPU cost proportional to node count
+
+### Risks
+- Node ID collisions (mitigated by NVS persistence since v0.5.0)
+- HashMap growth without cleanup (mitigated by stale-node eviction)
+
+## References
+
+- Issue #249: Detection window same regardless (24 comments)
+- Issue #237: Same display for 0/1/2 people (12 comments)
+- Issue #276: Only one can be detected (8 comments)
+- Issue #282: Detection fail (5 comments)
+- PR #295: Hysteresis smoothing (partial mitigation)
+- PR #300: ESP32 offline detection after 5s
+- ADR-062: QEMU Swarm Configurator