Fix active adapter detection for text encoders

[Subodh-17]

Summary

Fixes an issue where get_active_adapters() returns an empty list when a LoRA adapter is attached only to a text encoder.

get_active_adapters() previously only inspected ModelMixin components, while text encoders inherit from PreTrainedModel. This change includes both component types, matching the behavior already used by other LoRA adapter methods.

Testing

• Added test_get_active_adapters_text_encoder_only
• Focused regression test passes
• Relevant LoRA loader tests pass
• git diff --check passes

Fixes #14955

[sayakpaul]

Let's wait for #14965 to get merged first.

[HuggingFaceDocBuilderDev]

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[BenjaminBossan]

Thanks for fixing this, I confirmed that the test fails without the fix.

[sayakpaul]

@Subodh-17 #14965 removes this monolithic tests/lora/utils.py tester. Could we move it to https://github.com/huggingface/diffusers/blob/122b1e11fd497c3eeef14b3b98ca26a60166e48b/tests/pipelines/testing_utils/lora.py ?

[sayakpaul]

/diffusers-bot pytest tests/pipelines -k "test_get_active_adapters_text_encoder_only"

[github-actions]

✅ pytest tests/pipelines -k "test_get_active_adapters_text_encoder_only" passed on GPU — view logs.