### wai-quantum 0.6.1: the CUDA member's tensor-core kernel, and the Metal member

Additive. Every pinned digest is unchanged.

- **Every product on the tensor cores** (`quantum_fabric::cuda::TENSOR_SOURCE`,
  `tensor_limbs.cu`; `CudaMember::tensor`): a second CUDA kernel for the same gate, for
  devices of compute capability 8.0 or later (`DeviceIdentity::has_tensor_cores`). Each
  32-bit value is four 8-bit limbs in bf16, the lower three unsigned and the top one
  signed. One warp multiplies sixteen pairs' limbs by the gate's limb weights (sixteen
  products per pair, seven coefficients each) in fourteen `m16n8k16` steps, accumulated in
  f32. Every limb product is at most `2^16` and every coefficient sums at most four, so f32
  holds every partial sum exactly in any order. The kernel adds the coefficients, shifted
  into place, in 64-bit integers; the rest is the other kernel's arithmetic on exact
  products. The member id is the device's; the implementation id is the kernel's own
  (`cuda-tensor-limbs8/…`), and the member is probed before it is returned. A device below
  8.0 is `CudaError::Unsupported` (new). Seven mutants (`TENSOR_MUTANTS`), one of which is
  nine-bit limbs, which bf16 does not hold.
- **Measured** on the discrete GPU (compute capability 8.9, silicon): 66020 probe pairs
  agree, all four pinned certificates, circuits to 22 qubits match native, 7 of 7 mutants
  killed. The other kernel and the state vector are unchanged there (all four pins, 6 of 6
  and 4 of 4 mutants). CI: a step of `wai-quantum-cuda`; its absent leg runs the new tests
  over no device.
- **The Metal member** (`quantum_fabric_metal`, opt-in, macOS): the gate on the platform's
  GPU through its own interface, compiled at run time by the operating system's compiler.
  Two kernels, each with its own implementation id and mutants:
  - `lanes64.metal` (`metal-lanes64/…`): the CUDA kernel's exact 64-bit integer arithmetic
    in the Metal shading language, one serial dispatch per gate in one command buffer, the
    state in memory the GPU and the host share;
  - `matrix_limbs.metal` (`metal-matrix-limbs8/…`, `MetalMember::matrix`): every product
    formed by the GPU's SIMD-group matrix multiply, from 8-bit limbs in bf16 accumulated in
    f32, by the tensor-core kernel's argument. One SIMD group multiplies eight pairs' limbs
    by the gate's limb weights in fourteen 8 × 8 column blocks, and each thread joins its
    four products and forms one row. A device below GPU family 1007 is
    `MetalError::Unsupported`.

  A device is keyed by its GPU family number (`gpu-msl-<family>`), and its member id binds
  the device, its registry id, family and memory, and the operating system's version. Off
  macOS the member builds, finds nothing and says why.
- **Measured** on the macOS runner's GPU (family 1009, silicon): both kernels 9/9, each
  with 66020 probe pairs, all four pinned certificates and circuits to 22 qubits; 6 of 6
  and 7 of 7 mutants killed. Nine-bit limbs break 297 of the 484 edge pairs, so the
  multiply takes bf16 inputs. CI: `wai-quantum-metal`, on that runner, and its absent leg
  on Linux.
- **Measured by hand, outside CI:**
  - the gate as a portable tensor program, through XLA on a cloud tensor processor: the
    gate's module exact and its three mutants failing where they should, and the limb
    program (`stablehlo::limb_module`) exact on the processor's matrix unit, with the
    nine-bit set differing as it must;
  - `wai-quantum-qpu`'s `native_turns` against the service's simulator, no hardware used:
    with no noise, statistical parity at fidelity 1.0 on both gatesets' corpora (16
    circuits of 5 qubits, 1000 shots each), which checks the compilation to the service's
    native gates and the wire contract; with one of the service's device noise models,
    fidelity 0.909 (V1) and 0.927 (V2).

