Add Qwen Adapter unit tests

[has9800]

Description

Adds unit tests for the Qwen (Qwen-1) architecture adapter.

New file covers:

• Config flags the adapter sets (RMS norm, rotary embeddings, gated MLP, final
  RMS, attn_only)
• Component mapping for the TransformerLens canonical names to Qwen HF module paths,
  and bridge types for each entry
• Weight-processing conversion keys (q/k/v/o) and the HF source weights they
  read from
• _split_qkv_matrix splitting Qwen's fused c_attn projection back into
  separate q/k/v projections, covering the standard [3*d_model, d_model] layout,
  the Conv1D style [d_model, 3*d_model] layout, no-bias path, and an
  invalid-shape error. All work, all tests pass
• Factory registration for QwenForCausalLM resolves to QwenArchitectureAdapter

Contributes to #1302

Type of change

• Test addition

Checklist:

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have not rewritten tests relating to key interfaces which would affect backward compatibility