v0.7.0

Added

• CUDA kth-order Taylor evaluation: CudaContext::taylor_forward_kth_batch and taylor_forward_kth_batch_f64 support K=1..5 Taylor jet evaluation, bringing CUDA to parity with wgpu. Kernels are lazy-compiled on first use via taylor_codegen::generate_taylor_cuda.
• taylor_forward_kth_batch on GpuBackend trait: promoted from inherent method to trait method, enabling generic GPU STDE code to use arbitrary-order Taylor evaluation on either backend.
• taylor_forward_2nd_batch default trait impl: delegates to taylor_forward_kth_batch(order=3), eliminating duplicated logic across both backends.
• CUDA Taylor opcode test parity: gpu_stde.rs refactored with opcode_tests_for_backend! macro to run all per-opcode Taylor tests on both wgpu and CUDA.

Removed

• Handwritten taylor_eval.cu (527 lines): replaced by codegen K=3 output. The CUDA backend now uses taylor_codegen::generate_taylor_cuda for all Taylor kernels.
• Handwritten taylor_forward_2nd.wgsl (570 lines): replaced by codegen K=3 output. The wgpu backend now uses taylor_codegen::generate_taylor_wgsl for all Taylor shaders.
• cuda_taylor_fwd_2nd_body! macro: no longer needed since taylor_forward_2nd_batch delegates to the kth-order path.

Changed

• TrustRegionConfig (echidna-optim): new min_radius: F field added in 0.6.0 (breaking for direct struct construction; Default impls provide it).