feat(adr-185): P1 AETHER bindings (wifi_densepose.aether) + parity harness

Bind the ADR-024 contrastive CSI embedding surface into the wheel behind
a gated [aether] extra / Cargo `aether` feature, per ADR-185 section 3.2.

Surface (bound against the REAL code at HEAD, not the ADR wishlist):
- AetherConfig       -> EmbeddingConfig {d_model,d_proj,temperature,normalize}
- CsiAugmenter       -> augment_pair(window, seed)
- EmbeddingExtractor -> embed(csi): 128-dim L2-normed, GIL-released
- info_nce_loss, cosine_similarity (module fns)

ADR-185 section 3.2 also names aether_loss/VICReg components,
alignment_metric, uniformity_metric, forward_dual, and vicreg_* config
fields. None exist in embedding.rs at HEAD, so they are intentionally NOT
bound (a Rust-side gap, not a binding gap) rather than fabricated.

Parity (section 4.1, release-blocking): committed fixture
aether_input.json -> native Rust reference (tests/aether_parity.rs, calls
sensing-server EmbeddingExtractor directly) locks
tests/golden/aether_embedding.sha256; pytest (tests/test_aether.py) runs
the same fixture through the binding and asserts the identical SHA-256 of
the LE f32 bytes. Both pass.

Verified: cargo test --features aether --test aether_parity -> 2/2 pass;
maturin develop --features aether + pytest tests/test_aether.py -> 9/9
pass; default cargo build clean with 0 sensing-server refs in the dep
graph (gate keeps the base wheel lean).

HONEST WHEEL-SIZE FINDING (ADR-185 section 9 / Open Q 11.1, unresolved):
wifi-densepose-sensing-server is an Axum/tokio crate whose tokio/axum/
worldgraph/ruvector deps are NON-optional (only mqtt/matter are
features), so default-features=false does NOT drop them. An [aether]
wheel therefore links the full server tree and BREAKS the ADR-117 section
5.4 <=5 MB budget. The fix is the ADR-sanctioned hoist of embedding.rs
(+ its graph_transformer/sona siblings) into a leaf crate so the wheel
links pure compute only -- a change INSIDE wifi-densepose-sensing-server,
owned by another agent this session, so deferred as a required
pre-release follow-up. P1 binds real code and proves parity today; the
hoist is a wheel-size optimization, not a functional blocker.

Note: building required initializing the worldgraph/rufield/ruvector
submodules (absent in the fresh worktree).

python/wifi_densepose/aether.py

@@ -0,0 +1,47 @@
+"""AETHER — contrastive CSI embeddings & re-identification (ADR-024, ADR-185 P1).
+
+Self-supervised 128-dim L2-normalized embeddings for WiFi CSI: room
+fingerprinting, person re-identification, and anomaly scoring, computed
+entirely offline by the Rust core (no server, no network).
+
+Available **only** when the wheel was built with the ``[aether]`` extra::
+
+    pip install wifi-densepose[aether]
+
+Quick start::
+
+    from wifi_densepose.aether import AetherConfig, EmbeddingExtractor, cosine_similarity
+
+    ext = EmbeddingExtractor(n_subcarriers=56, config=AetherConfig())
+    a = ext.embed(window_a)          # list[float], length == config.d_proj (128)
+    b = ext.embed(window_b)
+    score = cosine_similarity(a, b)  # re-ID similarity in [-1, 1]
+"""
+
+from __future__ import annotations
+
+from wifi_densepose import _native
+
+# The AETHER symbols are compiled into `_native` only under the Rust
+# `aether` feature. In a base (`pip install wifi-densepose`) wheel they
+# are absent — surface a clear, actionable error naming the extra
+# (ADR-185 §6 acceptance criterion).
+if not hasattr(_native, "AetherConfig"):
+    raise ImportError(
+        "wifi_densepose.aether is not available in this wheel. "
+        "It requires the 'aether' extra:  pip install wifi-densepose[aether]"
+    )
+
+AetherConfig = _native.AetherConfig
+CsiAugmenter = _native.CsiAugmenter
+EmbeddingExtractor = _native.EmbeddingExtractor
+info_nce_loss = _native.info_nce_loss
+cosine_similarity = _native.cosine_similarity
+
+__all__ = [
+    "AetherConfig",
+    "CsiAugmenter",
+    "EmbeddingExtractor",
+    "info_nce_loss",
+    "cosine_similarity",
+]