Add 23 new operators for 2026 Spring Qiyuan AI Competition (T1-1-1)

[YZYY95K]

Summary

This PR adds 23 new operators to ntops as part of the 2026 Spring Qiyuan AI Competition.

New Operators

Activation Functions:

• leaky_relu, hardswish, hardtanh, elu, selu, mish, softplus, softsign, tanhshrink, relu6, prelu

Reduction Operators:

• log_softmax (with FP16/FP32 support)

Backward Operators:

• gelu_backward, sigmoid_backward, relu_backward, tanh_backward

Utility Operators:

• where, cast, log, sqrt, reciprocal, ceil, floor

Key Features

• All operators support both FP16 and FP32 with proper type casting for numerical stability
• FP16 operators use float32 intermediate computation to avoid precision issues
• 232 tests passing across all operators

Testing

All operators have been tested with multiple shapes and dtypes:

• Shapes: (128,), (16, 128), (2, 16, 128), (2, 4, 16, 128)
• Dtypes: float32 (rtol=0.001), float16 (rtol=0.01)

Team: YZYY95K