Function calcWorkgroups

Calculates the number of workgroups to dispatch, clamped to the device's maxComputeWorkgroupsPerDimension limit (default 65535 across most devices).

• 1D (pass only rows): returns a single count for dispatchWorkgroups(n).
• 2D (pass both rows and cols): returns { x, y } for dispatchWorkgroups(x, y). rows maps to the y dimension and cols maps to the x dimension.