* [TileOP] Add SM70 GEMM FMA fallback
* [TileOP] GemmFMA: drop redundant pre-staging sync and add docstrings
Address PR #2279 review:
- coderabbitai nit: the T.sync_threads() before the cooperative A/B stage
loads is unnecessary because A_stage / B_stage are freshly allocated
shared buffers — no other thread holds references to them, and the
later sync before the GEMM compute is sufficient.
- Docstring Coverage pre-merge check: add module-, helper-, method-, and
prim_func-level docstrings so coverage clears the 80% threshold.
No behavior change; the prim_func still stages through shared memory and
accumulates via scalar FMA. SM70 pytest trio still expected to pass.
* [TileOP] Harden SM70 GemmFMA fallback
* [TileOP] Fix SM70 FMA staging dtypes
* [TileOP] Tighten SM70 MMA dispatch for transposed A
