fix conversion error when processing tensorblock-TinyStories-656K GGUF

[daofazhiran]

Original main branch source (gguf_to_hf.py) does not handle tensorblock-TinyStories-656K GGUF.
This fix (edited by DeekSeek V4 Pro) make it run.

Following comments by DS4

修复了 fanfu 的两个问题：

• gguf_to_hf.py:258 — arch = field.parts[0] 取错字段导致 json 序列化失败，改为 field.contents()
• tensor 命名 — GGUF 命名（blk.0.attn_q.weight）重映射为 HF 命名（model.layers.0.self_attn.q_proj.weight）