Replace kinect-one with libfreenect2 bindings; Kinect v2 capture works on Windows too

kinect-one turned out not to compile off Linux (its isochronous USB is
a Linux-only nusb fork), which silently turned kinect-view's Windows
target into a viewer-only build. The Kinect v2 driver is now upstream
libfreenect2 — the battle-tested reference that kinect-one itself is a
translation of — linked through a new kinect2-sys crate:

- kinect2-sys: a C shim over the libfreenect2 C++ API (open, sync
  color+depth listener, registration, factory IR intrinsics) with
  hand-written externs — no bindgen, so no libclang requirement. The
  shim catches all C++ exceptions and reports through a thread-local
  buffer; the safe side covers Device/Listener/Registration with
  borrow-checked frame views. Built and linked via FREENECT2_DIR
  (Windows) or pkg-config (Linux).
- capture: the worker drives libfreenect2 (CPU depth pipeline,
  registered RGB at depth resolution with runtime BGRX/RGBX
  reordering, float-millimetre depth); the webcams (nokhwa) and the
  whole device stack are cross-platform again.
- verified in the container: libfreenect2 builds and installs
  (documented steps are exactly what the container runs), the shim
  links, the no-device path fails clearly; 84 tests pass. Windows
  cross-checks: x86_64-pc-windows-gnu fully green; aarch64-pc-
  windows-msvc green for all our crates (third-party mozjpeg-sys —
  the webcams' MJPEG decoder — mis-detects features under the
  clang-cl cross-toolchain but compiles with native MSVC).
- README documents the full dependency setup for Windows (UsbDk or
  libusbK driver, libusb, TurboJPEG, CMake build, FREENECT2_DIR,
  runtime DLLs) and Linux (apt packages, build+install, udev rule).
- PLAN.md: risk 1 resolved, capture pipeline and layout now name
  libfreenect2/kinect2-sys