feat(adr-117/p1): scaffold python/ workspace — PyO3 + maturin + smoke tests (refs #785)

ADR-117 P1 — the python/ directory is now a working maturin-buildable
crate that produces the v2.x replacement for the legacy pure-Python
wifi-densepose==1.1.0 PyPI wheel.

## What lands

- `python/Cargo.toml` — PyO3 0.22 with `extension-module` + `abi3-py310`
  (one binary covers Python 3.10–3.13 per OS/arch — keeps the
  cibuildwheel matrix to 5 wheels per release, not 20). Depends on
  `wifi-densepose-core` from the existing v2/ workspace via relative
  path.

- `python/pyproject.toml` — maturin>=1.7 build backend with
  `python-source = "python"` and `module-name = "wifi_densepose._native"`
  so the compiled module loads as an internal underscore-private
  submodule of the user-facing `wifi_densepose` package. PEP 621
  metadata + classifiers + project URLs. Optional-deps:
  `wifi-densepose[client]` for the P4 WS/MQTT pure-Python layer,
  `wifi-densepose[dev]` for the test toolchain (pytest, ruff, mypy).

- `python/src/lib.rs` — minimal `#[pymodule] wifi_densepose_native`
  exporting `__rust_version__`, `__rust_build_tag__`,
  `__build_features__`, and a `hello()` smoke function. P2 will land
  the core type bindings here.

- `python/wifi_densepose/__init__.py` — pure-Python facade re-exporting
  the compiled module's symbols under their stable user-facing names.
  Docstring teaches the v1→v2 migration story up-front.

- `python/wifi_densepose/py.typed` — PEP 561 marker so `mypy --strict`
  in user code treats the wheel as fully typed (real stubs land in P2).

- `python/tests/test_smoke.py` — 6 P1 acceptance tests:
  1. package imports without error
  2. version string is PEP 440-compliant
  3. `__rust_version__` is reachable from Python (the diagnostic
     surface ADR-117 §5.2 promised)
  4. `__build_features__` lists `p1-scaffold` marker
  5. `wifi_densepose.hello()` returns "ok" (FFI round-trip)
  6. `wifi_densepose._native` is reachable but the leading underscore
     conveys "private; users should import the parent package"

- `python/README.md` — phase ledger, local build instructions
  (`maturin develop`), layout diagram.

## What's deferred to P2+

- Core type bindings (`CsiFrame`, `Keypoint`, `PoseEstimate`) — P2
- Vitals + signal DSP bindings + witness v2 — P3
- Pure-Python WS/MQTT client layer (`wifi_densepose[client]`) — P4
- cibuildwheel + PyPI publish — P5
- v1.99.0 tombstone — concurrent with P5

The new `python/` crate is intentionally OUTSIDE the v2/ Cargo
workspace — it has its own Cargo.toml with `[package]` not
`[workspace.package]` inheritance — to keep maturin's `python-source`
+ `module-name` config self-contained and to avoid forcing every
`cargo test --workspace` invocation in v2/ to compile pyo3.

Refs ADR-117 §5 (Detailed design) and §6 (Phased migration).
Refs #785 (tracking issue).

Co-Authored-By: claude-flow <ruv@ruv.net>

python/pyproject.toml

@@ -0,0 +1,97 @@
+# ADR-117 — `wifi-densepose` v2.x PyPI wheel
+#
+# This is the PyO3+maturin replacement for the legacy pure-Python
+# `wifi-densepose==1.1.0` (last release 2025-06-07). One compiled
+# extension module per OS/arch covers Python 3.10–3.13 via abi3.
+
+[build-system]
+requires = ["maturin>=1.7,<2.0"]
+build-backend = "maturin"
+
+[project]
+name = "wifi-densepose"
+version = "2.0.0a1"
+description = "WiFi-based human pose estimation, vital sign extraction, and ambient intelligence from Channel State Information (CSI). PyO3 bindings for the Rust core."
+readme = "README.md"
+requires-python = ">=3.10"
+license = { text = "MIT" }
+authors = [
+    { name = "rUv", email = "ruv@ruv.net" },
+]
+keywords = [
+    "wifi", "csi", "pose-estimation", "vital-signs",
+    "biometric", "ambient-intelligence", "home-assistant", "matter",
+]
+classifiers = [
+    "Development Status :: 3 - Alpha",
+    "Intended Audience :: Developers",
+    "Intended Audience :: Science/Research",
+    "License :: OSI Approved :: MIT License",
+    "Operating System :: OS Independent",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
+    "Programming Language :: Rust",
+    "Topic :: Scientific/Engineering",
+    "Topic :: Scientific/Engineering :: Artificial Intelligence",
+    "Topic :: Scientific/Engineering :: Image Recognition",
+    "Topic :: System :: Hardware",
+    "Typing :: Typed",
+]
+dependencies = []
+
+[project.optional-dependencies]
+# ADR-117 §5.6 — pure-Python WS/MQTT client. Lands in P4.
+client = [
+    "websockets>=12.0",
+    "paho-mqtt>=2.1",
+]
+# Developer dependencies for running the test suite + lint.
+dev = [
+    "pytest>=8.0",
+    "pytest-asyncio>=0.23",
+    "ruff>=0.7",
+    "mypy>=1.13",
+]
+
+[project.urls]
+Homepage = "https://github.com/ruvnet/RuView"
+Repository = "https://github.com/ruvnet/RuView"
+Issues = "https://github.com/ruvnet/RuView/issues"
+Documentation = "https://github.com/ruvnet/RuView/tree/main/docs"
+"ADR-117 (modernization plan)" = "https://github.com/ruvnet/RuView/blob/main/docs/adr/ADR-117-pip-wifi-densepose-modernization.md"
+"Release notes (v0.7.0)" = "https://github.com/ruvnet/RuView/blob/main/docs/releases/v0.7.0-mqtt-matter.md"
+
+# Console-script entry points wired up in P5 once the CLI shim exists.
+# [project.scripts]
+# wifi-densepose = "wifi_densepose.cli:main"
+
+[tool.maturin]
+# Layout: ./python/ holds the Rust crate + Python facade; the wheel
+# packs `wifi_densepose/` as the top-level package.
+python-source = "python"
+module-name = "wifi_densepose._native"
+features = ["pyo3/extension-module"]
+# Strip debug symbols for smaller release wheels (ADR-117 §5.4 5 MB budget).
+strip = true
+
+[tool.pytest.ini_options]
+minversion = "8.0"
+testpaths = ["tests"]
+addopts = "-v --strict-markers"
+asyncio_mode = "auto"
+
+[tool.ruff]
+line-length = 100
+target-version = "py310"
+
+[tool.ruff.lint]
+select = ["E", "F", "W", "I", "UP", "B"]
+
+[tool.mypy]
+python_version = "3.10"
+strict = true
+warn_unused_ignores = true
+warn_redundant_casts = true