[Denverjin]

Allow eligible Ascend GM-to-UB copies to issue a DMA call when the runtime burst count is zero via T.copy(..., annotations={"emit_zero_burst": True}). This supports pair gathers with a runtime count of 0 or 2 without the surrounding count guard; zero bursts preserve existing UB contents.

The option uses the existing annotation decoder and requires an unpadded copy outside SimtVF, fixed positive row bytes, and a row count that captures every empty-region condition. Callers supply hardware-valid counts and address/stride expressions safe to evaluate for zero rows. Default copy behavior is unchanged.

Validation:

• Ascend copy lowering and bounds tests: 94 passed.
• Ascend DMA tests on dav-3510 / CANN 9.2.0: 11 passed, including zero-burst preservation with runtime strides.
• Linked ELF inspection through asckit/Bisheng: the opt-in copy retains the DMA instruction and removes its conditional jump.
• Repository formatting and static checks passed for all five changed files.

PR229 end-to-end performance was not remeasured.