feat(ruvector): implement ADR-017 as wifi-densepose-ruvector crate + fix MAT warnings

New crate `wifi-densepose-ruvector` implements all 7 ruvector v2.0.4
integration points from ADR-017 (signal processing + MAT disaster detection):

signal::subcarrier   — mincut_subcarrier_partition (ruvector-mincut)
signal::spectrogram  — gate_spectrogram (ruvector-attn-mincut)
signal::bvp          — attention_weighted_bvp (ruvector-attention)
signal::fresnel      — solve_fresnel_geometry (ruvector-solver)
mat::triangulation   — solve_triangulation TDoA (ruvector-solver)
mat::breathing       — CompressedBreathingBuffer 50-75% mem reduction (ruvector-temporal-tensor)
mat::heartbeat       — CompressedHeartbeatSpectrogram tiered compression (ruvector-temporal-tensor)

16 tests, 0 compilation errors. Workspace grows from 14 → 15 crates.

MAT crate: fix all 54 warnings (0 remaining in wifi-densepose-mat):
- Remove unused imports (Arc, HashMap, RwLock, mpsc, Mutex, ConfidenceScore, etc.)
- Prefix unused variables with _ (timestamp_low, agc, perm)
- Add #![allow(unexpected_cfgs)] for onnx feature gates in ML files
- Move onnx-conditional imports under #[cfg(feature = "onnx")] guards

README: update crate count 14→15, ADR count 24→26, add ruvector crate
table with 7-row integration summary.

Total tests: 939 → 955 (16 new). All passing, 0 regressions.

https://claude.ai/code/session_0164UZu6rG6gA15HmVyLZAmU

rust-port/wifi-densepose-rs/Cargo.toml

@@ -15,6 +15,7 @@ members = [
     "crates/wifi-densepose-sensing-server",
     "crates/wifi-densepose-wifiscan",
     "crates/wifi-densepose-vitals",
+    "crates/wifi-densepose-ruvector",
 ]
 
 [workspace.package]
@@ -120,6 +121,7 @@ wifi-densepose-config = { version = "0.1.0", path = "crates/wifi-densepose-confi
 wifi-densepose-hardware = { version = "0.1.0", path = "crates/wifi-densepose-hardware" }
 wifi-densepose-wasm = { version = "0.1.0", path = "crates/wifi-densepose-wasm" }
 wifi-densepose-mat = { version = "0.1.0", path = "crates/wifi-densepose-mat" }
+wifi-densepose-ruvector = { version = "0.1.0", path = "crates/wifi-densepose-ruvector" }
 
 [profile.release]
 lto = true