docs: add iPhone LiDAR integration guide

integrations/iphone-lidar/README.md

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+# RuView iPhone LiDAR
+
+This integration turns a LiDAR capable iPhone into a RuView geometry sensor and exposes the stream to any modern browser.
+
+## Architecture
+
+```text
+iPhone LiDAR
+  -> ARKit sceneDepth
+  -> depth + confidence + camera intrinsics + device pose
+  -> compact u16 millimeter wire frame
+  -> WebSocket relay
+  -> browser point cloud
+  -> future RuView HAL / fusion ingest
+```
+
+The native path is the sensor. The web path is a receiver and visualization surface. Mobile Safari does not expose ARKit scene depth directly to ordinary web pages, so the browser cannot replace the native capture layer on iPhone today.
+
+## Native iPhone path
+
+Create an iOS SwiftUI app target in Xcode, deployment target iOS 17 or newer, then add the files under `native/RuViewLiDAR/` to the target.
+
+Add this Info.plist value:
+
+```xml
+<key>NSCameraUsageDescription</key>
+<string>RuView uses the camera and LiDAR scanner to capture local depth geometry.</string>
+```
+
+Run on a physical LiDAR capable iPhone or iPad. The simulator does not provide LiDAR scene depth.
+
+The app requests `ARWorldTrackingConfiguration` with `.sceneDepth`, checks `supportsFrameSemantics`, extracts `ARDepthData.depthMap` and `confidenceMap`, and never transmits RGB camera frames.
+
+## Browser path
+
+```bash
+cd integrations/iphone-lidar/web
+npm install
+npm test
+npm start
+```
+
+Open `http://HOST:8787` in a browser. In the iPhone app set the endpoint to:
+
+```text
+ws://HOST:8787/ws/lidar
+```
+
+For production use TLS and `wss://`.
+
+## Wire format
+
+Schema: `ruview.lidar.depth.v1`
+
+Depth is downsampled by 2 in each dimension by default and streamed at a maximum of 15 FPS. Each depth sample is encoded as little endian UInt16 millimeters plus one UInt8 confidence value. This reduces the depth payload from roughly 196 KB per 256 x 192 Float32 frame to roughly 37 KB per 128 x 96 frame before base64 and JSON overhead.
+
+At 15 FPS that is approximately 0.75 MB/s after base64 overhead, versus roughly 8 MB/s for uncompressed Float32 JSON at full resolution.
+
+## Privacy and governance
+
+The initial implementation labels provenance as `source=live` and `privacyClass=geometry-only`. It sends depth geometry, confidence, camera intrinsics, pose, sequence, and wall clock timestamp. It does not send RGB imagery.
+
+Production integration should terminate the WebSocket inside RuView, authenticate the device using the existing sensor identity path, convert each frame into `ruview-hal::Observation`, and attach witness receipts before fusion or persistence.
+
+## Acceptance test
+
+1. Run the relay and browser viewer.
+2. Run the native app on a LiDAR capable iPhone.
+3. Start LiDAR capture and enable streaming.
+4. Move the phone through a room.
+5. Verify the browser shows a changing point cloud, sequence increases monotonically, latency stays below 150 ms on a local WiFi network, and no RGB payload is present in captured WebSocket frames.