feat: ADR-024 Contrastive CSI Embedding Model — all 7 phases (#52)

Full implementation of Project AETHER — Contrastive CSI Embedding Model.

## Phases Delivered
1. ProjectionHead (64→128→128) + L2 normalization
2. CsiAugmenter (5 physically-motivated augmentations)
3. InfoNCE contrastive loss + SimCLR pretraining
4. FingerprintIndex (4 index types: env, activity, temporal, person)
5. RVF SEG_EMBED (0x0C) + CLI integration
6. Cross-modal alignment (PoseEncoder + InfoNCE)
7. Deep RuVector: MicroLoRA, EWC++, drift detection, hard-negative mining, SEG_LORA

## Stats
- 276 tests passing (191 lib + 51 bin + 16 rvf + 18 vitals)
- 3,342 additions across 8 files
- Zero unsafe/unwrap/panic/todo stubs
- ~55KB INT8 model for ESP32 edge deployment

Also fixes deprecated GitHub Actions (v3→v4) and adds feat/* branch CI triggers.

Closes #50

rust-port/wifi-densepose-rs/crates/wifi-densepose-core/README.md

@@ -0,0 +1,83 @@
+# wifi-densepose-core
+
+[![Crates.io](https://img.shields.io/crates/v/wifi-densepose-core.svg)](https://crates.io/crates/wifi-densepose-core)
+[![Documentation](https://docs.rs/wifi-densepose-core/badge.svg)](https://docs.rs/wifi-densepose-core)
+[![License](https://img.shields.io/crates/l/wifi-densepose-core.svg)](LICENSE)
+
+Core types, traits, and utilities for the WiFi-DensePose pose estimation system.
+
+## Overview
+
+`wifi-densepose-core` is the foundation crate for the WiFi-DensePose workspace. It defines the
+shared data structures, error types, and trait contracts used by every other crate in the
+ecosystem. The crate is `no_std`-compatible (with the `std` feature disabled) and forbids all
+unsafe code.
+
+## Features
+
+- **Core data types** -- `CsiFrame`, `ProcessedSignal`, `PoseEstimate`, `PersonPose`, `Keypoint`,
+  `KeypointType`, `BoundingBox`, `Confidence`, `Timestamp`, and more.
+- **Trait abstractions** -- `SignalProcessor`, `NeuralInference`, and `DataStore` define the
+  contracts for signal processing, neural network inference, and data persistence respectively.
+- **Error hierarchy** -- `CoreError`, `SignalError`, `InferenceError`, and `StorageError` provide
+  typed error handling across subsystem boundaries.
+- **`no_std` support** -- Disable the default `std` feature for embedded or WASM targets.
+- **Constants** -- `MAX_KEYPOINTS` (17, COCO format), `MAX_SUBCARRIERS` (256),
+  `DEFAULT_CONFIDENCE_THRESHOLD` (0.5).
+
+### Feature flags
+
+| Flag    | Default | Description                                |
+|---------|---------|--------------------------------------------|
+| `std`   | yes     | Enable standard library support            |
+| `serde` | no      | Serialization via serde (+ ndarray serde)  |
+| `async` | no      | Async trait definitions via `async-trait`   |
+
+## Quick Start
+
+```rust
+use wifi_densepose_core::{CsiFrame, Keypoint, KeypointType, Confidence};
+
+// Create a keypoint with high confidence
+let keypoint = Keypoint::new(
+    KeypointType::Nose,
+    0.5,
+    0.3,
+    Confidence::new(0.95).unwrap(),
+);
+
+assert!(keypoint.is_visible());
+```
+
+Or use the prelude for convenient bulk imports:
+
+```rust
+use wifi_densepose_core::prelude::*;
+```
+
+## Architecture
+
+```text
+wifi-densepose-core/src/
+  lib.rs          -- Re-exports, constants, prelude
+  types.rs        -- CsiFrame, PoseEstimate, Keypoint, etc.
+  traits.rs       -- SignalProcessor, NeuralInference, DataStore
+  error.rs        -- CoreError, SignalError, InferenceError, StorageError
+  utils.rs        -- Shared helper functions
+```
+
+## Related Crates
+
+| Crate | Role |
+|-------|------|
+| [`wifi-densepose-signal`](../wifi-densepose-signal) | CSI signal processing algorithms |
+| [`wifi-densepose-nn`](../wifi-densepose-nn) | Neural network inference backends |
+| [`wifi-densepose-train`](../wifi-densepose-train) | Training pipeline with ruvector |
+| [`wifi-densepose-mat`](../wifi-densepose-mat) | Disaster detection (MAT) |
+| [`wifi-densepose-hardware`](../wifi-densepose-hardware) | Hardware sensor interfaces |
+| [`wifi-densepose-vitals`](../wifi-densepose-vitals) | Vital sign extraction |
+| [`wifi-densepose-wifiscan`](../wifi-densepose-wifiscan) | Multi-BSSID WiFi scanning |
+
+## License
+
+MIT OR Apache-2.0