#1108 Add architecture check condition in native_dense.cpp

说明

Fixes a split-GGUF loading issue reproduced with Huihui-Qwen3.8-Flash-Next-abliterated-GGUF (UD-Q4_K_XL).

The first shard contains the full qwen4exp metadata, while later shards include general.architecture = qwen4exp but omit fields such as qwen4exp.block_count. Strata therefore re-validates the architecture on later shards and fails with:

native dense projections: missing qwen4exp.block_count

This change avoids repeating the full architecture check after it has already been successfully initialized from the first shard. The model loads and runs successfully after the fix.