Apply Qwen NFC normalization before token splitting

docs/issue116-nfc/compatible.output.log

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+
+running 1 test
+test engine::metal::qwen_mtplx::owner::issue111_product::issue111_token_prefix_cache ... ds4: Metal device Apple M5 Max, 128.00 GiB RAM
+ds4: Metal 4 tensor API enabled for Tensor kernels
+ds4: drift-patch flags hc_stable=on norm_unify=on kv_raw_f32=off rope_exp2_log2=off math_safe=off tensor_matmul=on
+ds4: Qwen reference kernels: Powered by MTPLX — https://github.com/youssofal/mtplx
+[qwen4_exp] ngram table: streamed from SSD (file-backed pages, hot cache 1023M, prefetch on) — resident only at >=160G RAM or MTPLX_NGRAM_RESIDENT=1
+[mtplx] verify SDPA head-chunked: q_len=24 heads_per_chunk=1 chunks=24
+{"case":"token_cache","old_tokens":89,"new_tokens":93,"old_prefix_miss":true,"warm_cached":95,"disk_cached":95,"warm_disk_state_exact":true}
+ok
+
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 554 filtered out; finished in 16.10s
+