LTX-2: decouple the RoPE time base from the playback frame rate (Slow-Motion-Control LoRA) #14980

What
Lightricks/LTX-2.5-22b-LoRA-Slow-Motion-Control expects the diffusion stage to be conditioned on fps / speed while the video keeps its real frame rate. Lightricks' distilled_speed_demo.py does exactly that. Without it, the LoRA gives no speed control.

Why frame_rate alone doesn't cover it
In the LTX-2 pipelines and modular blocks, frame_rate also sizes the generated audio (num_frames / frame_rate) and converts the duration head's seconds into frames. Setting it to fps / speed therefore shortens the audio and inflates the predicted frame count. On the tiny test pipeline, frame_rate=120 gives 9 audio tokens instead of 43, and 121 frames instead of 25 when num_frames is omitted.

Proposal
An optional conditioning_frame_rate (default: frame_rate) used only for the positional time axis: video, keyframe and reference coords, plus the transformer fps. Audio sizing, the duration head and the output keep following frame_rate. This is the split the DFR pipelines already make internally with conditioning_fps.

Implementation proposed in #14967. Does this scope (classic pipelines + modular blocks) look right to you?