Fix cuda_toolkit_check driver version and add cuda-bindings dep

[jayavenkatesh19]

Summary

Two related fixes surfaced while smoke-testing #137 on a fresh Brev box:

• cuda_toolkit_check was reading the kernel driver, not the CUDA driver. get_driver_version(kernel_mode=True) returns the NVIDIA kernel module version (e.g. 580 from 580.126.09), not the CUDA Driver API version (e.g. 13 from CUDA 13.0). The verbose message also printed Driver supports CUDA 580, which is what tipped this off. Dropping kernel_mode=True makes get_driver_version() default to the CUDA Driver API mode and the comparison logic actually fires.
• cuda-bindings is now declared as a runtime dep, and the conda recipe gets the missing cuda-core it should have had since Add CUDA toolkit check to rapids doctor #141. cuda-core calls into cuda.bindings.driver via lazy import and without cuda-bindings installed, cuda_toolkit_check raises ImportError: cuda.bindings 12.x or 13.x must be installed on a fresh pip install rapids-cli. The pin >=12.9.6,!=13.0.*,!=13.1.* excludes the cuda-bindings 13.0/13.1 wheels and is compatible with both CUDA 12 and CUDA 13 driver hosts (verified with cuda-bindings 12.9.6 against a CUDA 13 environment and cuda-bindings 13.2 against a CUDA 12 environment).

A regression test (test_gather_toolkit_info_driver_major_is_cuda_major) exercises _gather_toolkit_info() end-to-end and asserts driver_major < 100 to ensure that we are getting the CUDA major version and not the driver version

Closes #145.