feat(CK): Add gelu_tanh_and_mul to MoE GEMM

[jonahbernard]

Motivation

The fused MoE GEMM only supported gelu_and_mul (exact, erf-based) and
silu_and_mul activations. Models that use the tanh approximation of GELU
in their MoE experts (e.g. Gemma-family architectures) had no matching
activation in the CK fused MoE path. This PR adds gelu_tanh_and_mul so
those models can run their MoE layers on the CK gridwise MoE GEMM.

Technical Details

Adds a new activation gelu_tanh_and_mul = 3 to the MoE GEMM, computed via
the existing FastGelu functor (tanh approximation), alongside the existing
exact Gelu (gelu_and_mul = 0).

• Enum (gridwise_gemm_xdl_cshuffle_common.hpp): add
  gelu_tanh_and_mul = 3 to the activation enum.
• Kernel (gridwise_moe_gemm.hpp): add gelu_tanh_and_mul branches
  next to each existing gelu_and_mul site (4 sites: scaled/unscaled ×
  gate/up), applying FastGelu to the gate before the elementwise multiply.
  Reuses the same scale and pk_i4 handling as the silu/gelu paths.
• CPU reference (reference_moe_gemm.hpp): add an ActivationType == 3
  branch using the host FastGelu, mirroring the existing Silu/Gelu
  branches, so the new activation can be verified against an independent
  oracle. The static_assert is updated to allow {0, 1, 3}.
• Example/test (moe_gemm1_xdl_fp8_gelu_tanh.cpp + CMakeLists): a
  self-verifying example with ActOP = 3, registered as a smoke ctest.

Device and host both use FastGelu (the tanh approximation), so the
verification compares matching math.

Test Plan

Added example_moe_gemm1_xdl_fp8_gelu_tanh, a self-verifying example
(registered as a SMOKE_TEST ctest) that runs the gelu_tanh MoE GEMM on
device and checks the result against the CPU reference.

Built and run on gfx950 (ROCm 7.2.3):

  ctest -R example_moe_gemm1_xdl_fp8_gelu_tanh

  1/1 Test #259: example_moe_gemm1_xdl_fp8_gelu_tanh ... Passed  65.92 sec
  100% tests passed, 0 tests failed out of 1

Test Result

 ctest -R example_moe_gemm1_xdl_fp8_gelu_tanh -V
UpdateCTestConfiguration  from :/app/rocm-libraries-jonah/projects/composablekernel/build/DartConfiguration.tcl
Parse Config file:/app/rocm-libraries-jonah/projects/composablekernel/build/DartConfiguration.tcl
UpdateCTestConfiguration  from :/app/rocm-libraries-jonah/projects/composablekernel/build/DartConfiguration.tcl
Parse Config file:/app/rocm-libraries-jonah/projects/composablekernel/build/DartConfiguration.tcl
Test project /app/rocm-libraries-jonah/projects/composablekernel/build
Constructing a list of tests
Done constructing a list of tests
Updating test list for fixtures
Added 0 tests to meet fixture requirements
Checking test dependency graph...
Checking test dependency graph end
test 259
    Start 259: example_moe_gemm1_xdl_fp8_gelu_tanh

259: Test command: /app/rocm-libraries-jonah/projects/composablekernel/build/bin/example_moe_gemm1_xdl_fp8_gelu_tanh
259: Working Directory: /app/rocm-libraries-jonah/projects/composablekernel/build/example/65_gemm_multiply_multiply
259: Test timeout computed to be: 1500
259: a0_t_k: dim 2, lengths {16384, 6144}, strides {6144, 1} 
259: b0_e_n_k: dim 3, lengths {8, 6144, 8192}, strides {50331648, 1, 6144} 
259: d1_e_n: dim 2, lengths {8, 8192}, strides {8192, 1} 
259: d2_e_n: dim 2, lengths {32768, 4096}, strides {1, 0} 
259: d0_t_n: dim 2, lengths {16384, 4096}, strides {1, 16384} 
259: d2_e_n: dim 2, lengths {32768, 4096}, strides {1, 0} 
259: e_t_n: dim 3, lengths {16384, 2, 4096}, strides {8192, 4096, 1} 
1/1 Test #259: example_moe_gemm1_xdl_fp8_gelu_tanh ...   Passed   63.15 sec

The following tests passed:
        example_moe_gemm1_xdl_fp8_gelu_tanh

100% tests passed, 0 tests failed out of 1

Label Time Summary:
SMOKE_TEST    =  63.15 sec*proc (1 test)

Total Test time (real) =  63.17 sec

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

[therock-pr-bot]

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🧪 Unit Test	❌ Fail	Error: Source/code files changed without an accompanying unit test. Expected: add at least one test file named like test_<name>.py / test_<name>.cpp (or <name>_test.*). Current: code file(s) changed: projects/composablekernel/example/65_gemm_multiply_multiply/moe_gemm1_xdl_fp8_gelu_tanh.cpp, projects/composablekernel/include/ck/tensor_operation/gpu/grid/gridwise_gemm_xdl_cshuffle_common.hpp, projects/composablekernel/include/ck/tensor_operation/gpu/grid/gridwise_moe_gemm.hpp, projects/composablekernel/include/ck/tensor_operation/gpu/grid/gridwise_moe_mx_gemm.hpp, projects/composablekernel/include/ck/tensor_operation/gpu/grid/gridwise_moe_mx_gemm_bpreshuffle.hpp (+1 more); no test file found
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[aosewski]

@jonahbernard I've reached out to you internally. Basically I'd propose to use CK-Tile's moe gemm since it provides much more flexibility for customizations.