Add and verify the text-to-image path, and fix the UniPC flow_shift selection
it exposed.
Bug: the stage chose flow_shift by task (`3.0 if is_t2i else 10.0`). The
framework selects it purely by the named resolution bucket
(`OmniSampleArgs._RESOLUTION_SHIFT_DEFAULTS`, 8B backbone: 256->3.0, 480->5.0,
720/768->10.0); T2V/I2V/T2I share a shift at a given resolution. The task-based
rule only coincidentally matched (T2V@720, T2I@256). The canonical Cosmos3 T2I
is 960x960 (the "720" bucket -> 10.0), so `is_t2i->3.0` was wrong for real T2I.
- Replace with `_flow_shift_for_resolution(h, w)` mapping the longest side to the
framework bucket (<=320:3.0, 640-832:5.0, 960-1360:10.0), applied to all tasks.
- Parity: `test_cosmos3_flow_shift_parity.py` checks the mapping against the
framework's `{VIDEO,IMAGE}_RES_SIZE_INFO` x `_RESOLUTION_SHIFT_DEFAULTS` for
every (resolution, aspect) in the 8B rows (20 cases).
- Update the call-graph mode-dispatch tests for resolution-based shift.
Also harden `_image_to_video_tensor`'s tensor branch to respect the FastVideo
[-1,1] convention for already-preprocessed conditioning tensors (the PIL path,
used by the real pipeline, stays framework-exact and bit-parity-tested).
Example: `examples/inference/basic/basic_cosmos3_t2i_new_api.py` (num_frames=1,
960x960). Verified on B200 (real weights, 35 steps): a coherent red-panda image
matching the prompt, flow_shift=10.0. Full cosmos3 suite: 118 passed, 0 skipped.
SolitaryThinker
f13d017fc1