fix(inference): skip generation VAE for reasoner-only runs

[chrisvoncsefalvay]

Reasoner-only CLI inference to no longer instantiate the generation vision tokeniser or resolves the video VAE. Mixed and generative input sets retain the existing eager-loading behaviour.

Root cause

OmniMoTModel.set_up_tokenizers instantiated model.config.tokenizer unconditionally. For Cosmos3-Edge, that tokeniser resolves Wan2.2_VAE.pth, even when inference only produces reasoner text.

Changes

• detect all-reasoner input sets before model construction and apply a narrow model.config.load_vision_tokenizer=false override
• make the generation vision tokeniser optional only under that override; the default remains enabled
• use configured compression factors when no live tokeniser exists, covering network construction and token-budget batching
• treat separate vision-decode GPU placement as a no-op when the generation tokenizer is intentionally absent
• cover all-reasoner, mixed, empty, default-load, skip-load, batching, and separate-decode cases

Behaviour

• Reasoner-only inputs: the VLM processor and checkpoint-local vision tower still load; the generation VAE does not.
• Mixed or generative inputs: unchanged; the generation tokenizer follows the existing eager path.
• Other entry points: unchanged by default because load_vision_tokenizer defaults to true.

Fixes #128