Reject sparse MMA K tiles with unhandled tails - #3367

Summary

• Reject an SM80-style sparse MMA K tile whose extent is not divisible by the dtype-specific MMA K atom before the lowering floors its loop trip count.
• Add an SM90 compile regression for total K=192 with int8 block_K=96, where each tile would drop 32 elements even though total K is divisible by 64.

Fixes #2605.

Validation

• Ruff check/format, Python syntax compilation, and git diff --check pass.
• Focused pytest collection is blocked by the local Windows Python 3.13 environment: Home Assistant's pytest plugin imports cntl, which is unavailable on Windows. The TileLang test did not run.
• No local CUDA compiler/runtime or native TileLang build is available.

Summary

• GemmSPMMA.lower now raises ValueError when a sparse MMA K tile is not divisible by its dtype-specific K atom. This prevents the fallback loop from silently dropping the tile’s K tail.
• Added an SM90 regression test for int8 with total K=192 and block_K=96. It checks that compilation rejects the tile, although total K is divisible by the 64-element atom.

Validation

• Ruff checks and formatting, Python syntax compilation, and git diff --check reportedly pass.
• The regression test did not run. Pytest collection was blocked because the Home Assistant pytest plugin imports fcntl, which is unavailable in the local Windows Python 3.13 environment.
• No local CUDA compiler, runtime, or native TileLang build was available.