gpt-oss: rename arch "gptoss" -> "gpt-oss" (incl. KV prefix), inject
the missing `expert_feed_forward_length` from the ffn_gate_exps shape,
and rename `attn_out`/`attn_sinks`/`ffn_norm` tensors to upstream's
`attn_output`/`attn_sinks.weight`/`post_attention_norm`. Also remove
the library/gpt-oss -> dhiltgen/gpt-oss redirect now that the compat
shim handles it directly.
lfm2: rename `output_norm.weight` -> `token_embd_norm.weight` and fix
a stale `lfm2.feed_forward_length` (some Ollama blobs claim 12288 on
a model whose ffn_gate is [2048, 8192]) by reading the real value off
the ffn_gate tensor shape.
Adds two helpers to compat-util: `copy_kv` (type-preserving generic
KV copy) and `rename_kv_prefix` (bulk-copy every KV with a given
prefix to a new prefix). Old keys are left in place — harmless because
the loader queries by exact name and only the new prefix matters.
Tested locally: gpt-oss:20b and lfm2.5-thinking now load + generate
coherently against an unmodified upstream llama-server build.
d0f38a915a