补充 core/shard 与 custom_ops/experimental 的 UT 覆盖率

背景

HyperParallel 对单文件 UT 覆盖率有 ≥70% 的要求。当前以下文件覆盖率不达标：

此外，custom_ops/experimental/__init__.py 将实现与导出混写在同一文件，不符合模块分离约定。

目标

1. 重构 custom_ops/experimental：将 5 个 wrapper 函数的实现从 __init__.py 提取到 experimental_ops.py，__init__.py 保持纯 re-export，对外接口不变。

2. 补充 UT，使所有文件达到 ≥70% 覆盖率：

   • core/shard/api.py：新建 test_api.py，覆盖 hook 注册、layout 转换、DTensor 重分布路径
   • core/shard/custom_shard.py：新建 test_custom_shard.py，覆盖所有分支
   • core/shard/_op_dispatch.py：补充 test_op_dispatch.py，覆盖 LayoutCacheManager、_pack_infer_output、_with_layout_infer、dispatch 流程
   • ops/parallel_flash_attention_score.py：新建，覆盖 ParallelFlashAttention 各 layout 模式
   • ops/parallel_ops.py：新建，覆盖基类逻辑
   • ops/parallel_tuple_elementwise.py：新建，覆盖 layout 一致性推断
   • ops/parallel_scaled_dot_product_attention.py：补充，覆盖 get_expand_impl、causal mask
   • ops/parallel_embedding.py、ops/parallel_conv3d.py、ops/parallel_one_hot_ext.py：补充 get_expand_impl 路径
   • custom_ops/experimental/experimental_ops.py：新建 test_experimental_ops.py，100% 覆盖

所有 UT 使用 mock 平台，无 GPU/NPU 硬件依赖。

相关 PR

!665

schema_version: 1
source: gitcode
gitcode_repo: mindspore/hyper-parallel
gitcode_issue: 159
source_url: https://gitcode.com/mindspore/hyper-parallel/issues/159

Read the listed files under hyper_parallel/core/shard, core/shard/ops, and custom_ops/experimental, starting with custom_ops/experimental/init.py and the named UT entry points. Run the existing mock-platform tests and coverage checks to identify uncovered branches. Done means experimental_ops.py is covered at 100%, every listed file reaches at least 70%, and init.py preserves the public re-exports without hardware dependencies.