Fix Hadamard hook target-type collection for partial quantization with rotation

Summary

This PR fixes Hadamard online-hook registration for rotated models that are partially quantized. The set of down_proj target layer classes used for hook registration is now derived from the actual loaded/running model instead of from the recorded quant_method or from sampling the first down_proj layer. This ensures hooks land on the correct layers when a model contains a mix of quantized and unquantized (nn.Linear) down_proj layers, or multiple down_proj types — reventing degraded rotated-model inference.

Affected files: onecomp/quantized_model_loader.py, onecomp/runner.py, onecomp/pre_process/rotation_utils.py.

Changes

Bug fix

Fixed Hadamard online hook registration for rotation + partial quantization models. Previously the down_proj target layer classes were derived from the recorded quant_method (gptq/dbf/onebit), or by sampling the first down_proj layer's type. When a model is only partially quantized (mixed quantized / unquantized down_proj layers) or contains multiple down_proj types, hooks were registered on the wrong classes — either missing quantized layers or firing on plain nn.Linear — degrading rotated-model inference.

• Hadamard hook target types are now derived from the actual model instead of quant_method. Added collect_down_proj_types() and collect_quantized_down_proj_types() to rotation_utils.py.
• QuantizedModelLoader (loading from disk) uses collect_down_proj_types() to collect all distinct down_proj layer types from the loaded model, including nn.Linear when present (e.g. unquantized down_proj in a saved partial-quantization model); it intentionally does not filter nn.Linear.
• Runner hook re-registration (during a quantization run, where some down_proj may still be nn.Linear) uses collect_quantized_down_proj_types(), which excludes nn.Linear so unquantized down_proj layers do not receive hooks; it skips registration entirely when no quantized down_proj exists.

Test

• Added regression tests for Hadamard hook target-type collection, pinning down_proj type discovery for both full and partial quantization (tests/onecomp/runner/test_hadamard_hook_type_collection.py).