hybrid attention

Two point eight trillion parameters fits in one node, because the experts ship in a four-bit format. The footprint arithmetic that reproduces the project's own published hardware minimum, the hybrid cache that needs specific engine support, and why batch-one throughput is a tenth of the bound.

Most layers stop having a growing cache, which changes capacity planning by a large factor and demands a cache manager most engines did not have. What the memory model becomes, what the engine must implement, and the two features that were disabled by default while it settled.