nx_f32_transformer_test.nx

nx_f32_transformer_test.nx -- integration smoke. Zero-weight identity check: with all weights = 0 and gamma = 0, every matmul produces 0, every RMSNorm produces 0, both residual additions reduce to "x + 0 = x", so output should equal input unchanged. This is the structural-acceptance gate: proves the full chain of RMSNorm + matmul + softmax + SiLU + residual composes without crashing and preserves the identity at zero weights.