Branch: smla-only baseline before COMM_PROTOCOL_UBC_CTP ops

[yjyang62]

Summary

Creates a build-friendly branch for CANN 9.1.T560 / A5 environments that need up-to-date sparse_flash_mla without pulling in mc2 operators that require COMM_PROTOCOL_UBC_CTP (e.g. engram_fetch, moe_ep_dispatch).

Branch strategy

• Base: 24b77a54b ([flash_attn]整改torch extension目录) — last commit before COMM_PROTOCOL_UBC_CTP usage was introduced
• Cherry-picked on top:
  • dcd6dbdd2 — BSND padding + FlashDecode workspace fix for SMLA
  • 2b68f554e — SMLA stride array pointer fix for non-contiguous KV

What this branch includes

• Full sparse_flash_mla + sparse_flash_mla_metadata implementation
• A5 arch35 kernel support (from base)
• SMLA padding/workspace and stride fixes (cherry-picked)

What this branch excludes

• engram_fetch / engram_fetch_wait
• moe_ep_dispatch / moe_ep_combine
• elastic_buffer COMM_PROTOCOL integration
• Any other commits using COMM_PROTOCOL_UBC_CTP

Suggested build commands

git checkout cursor/smla-only-before-ubc-ctp-2c82
source /usr/local/Ascend/cann/set_env.sh

# SMLA-only custom package (recommended)
bash build.sh --pkg --soc=ascend950 \
  --vendor_name=custom \
  --ops=sparse_flash_mla,sparse_flash_mla_metadata -j8

# Or full ops-transformer package on this branch (no COMM_PROTOCOL ops)
bash build.sh --pkg --soc=ascend950 -j8

Conflict resolution note

Cherry-pick of 2b68f554e had doc/tiling conflicts; functional SMLA changes from that commit were kept.