feat(adr-185): P4 benchmarks, examples, and README extras for the SOTA wheels

ADR-185 §4.2 pytest-benchmark micro-benchmarks + runnable examples +
README extras table for the aether/meridian/mat bindings.

- python/bench/test_bench_{aether,meridian,mat}.py — follow the existing
  test_bench_vitals.py pattern (skipped by default; --benchmark-only).
- python/examples/{reid_from_csi,cross_room_calibrate,mat_triage}.py —
  typed, runnable, mypy --strict clean.
- python/README.md — SOTA extras table + example links.

Measured on a RELEASE wheel (maturin develop --release --features sota),
reference machine per ADR-117 §10:
  AETHER embed()          mean ~150 us/window   (target <2 ms)   PASS
    batch scaling 1/8/64: 140 / 1091 / 8509 us  (linear, no O(n^2)) PASS
  MERIDIAN normalize()    mean ~2.2 us/frame     (target <200 us) PASS
  MERIDIAN encode()       mean ~6.9 us           (target <200 us) PASS
  MAT ingest+scan_once()  mean ~40 ms/256-frame  (< 500 ms interval) PASS

Acceptance self-verification (ADR-185 §6), all run just now:
  §6.1 default wheel 279 KB (<=5 MB); build_features has no p6-* feature  PASS
  §6.2 pytest tests/test_aether.py    9/9   PASS
  §6.3 pytest tests/test_meridian.py  13/13 PASS
  §6.4 pytest tests/test_mat.py       7/7   PASS
  §6.5 benchmarks meet all targets (above)                                PASS
  §6.6 parity harness: 3/3 SHA golden gates green (cargo test --features
       sota, 6/6); CI *wiring* as a release gate is out of python/ scope  PARTIAL
  §6.7 SOTA accuracy bars on labeled fixtures: NOT met (no labeled
       fixtures / trained models available; parity proves path-equality,
       not accuracy)                                                       OPEN
  §6.8 .pyi stubs present for all three; mypy --strict on the 3 examples   PASS
  §6.9 base wheel `import wifi_densepose.{aether,meridian,mat}` raises a
       clear ImportError naming the extra                                  PASS
  No regression: 76 pre-existing tests pass on the default wheel.

Status NOT flipped to Accepted: §6.7 (accuracy bars) is unmet, §6.6 CI
wiring is pending, and the per-extra wheel-size hoists (sensing-server /
train / mat leaf crates) remain follow-ups. docs/adr/ is owned by another
agent this session, so the ADR ledger edit is deferred to that owner.

python/README.md

@@ -43,6 +43,29 @@ pip install "wifi-densepose[client]"       # + WebSocket/MQTT clients
 Wheels are published for Linux (x86_64, aarch64), macOS (x86_64, arm64), and
 Windows (amd64).
 
+### SOTA extras (ADR-185)
+
+Three optional subsystems bind the Rust SOTA modules as compiled-feature
+wheels. Each raises a clear `ImportError` if you import it without the extra:
+
+| Extra | Module | What it adds |
+|-------|--------|--------------|
+| `[aether]` | `wifi_densepose.aether` | Contrastive CSI embeddings / re-identification (ADR-024) — `EmbeddingExtractor`, `cosine_similarity`, `info_nce_loss` |
+| `[meridian]` | `wifi_densepose.meridian` | Cross-environment domain generalization (ADR-027) — `HardwareNormalizer`, `GeometryEncoder`, `RapidAdaptation`, `CrossDomainEvaluator` |
+| `[mat]` | `wifi_densepose.mat` | Mass-Casualty Assessment disaster-survivor detection + START triage — `DisasterResponse`, `Survivor`, `TriageStatus` |
+| `[sota]` | all three | Convenience superset |
+
+```bash
+pip install "wifi-densepose[aether]"       # re-identification embeddings
+pip install "wifi-densepose[meridian]"     # cross-room calibration
+pip install "wifi-densepose[mat]"          # disaster triage
+pip install "wifi-densepose[sota]"         # all three
+```
+
+Runnable examples: [`examples/reid_from_csi.py`](examples/reid_from_csi.py),
+[`examples/cross_room_calibrate.py`](examples/cross_room_calibrate.py),
+[`examples/mat_triage.py`](examples/mat_triage.py).
+
 ## Usage
 
 ### Extract breathing rate from a CSI stream