BSAI Qwen image 2.1 Sampler

BSAI Qwen image 2.1 sampler: all KSampler parameters (seed/steps/CFG/sampler/scheduler/denoise) are kept as widgets, and each can be right-clicked 'Convert widget to input' to wire an upstream node (e.g. the enhancer's RECOMMENDED_STEPS/CFG). Adds optional guider / sigmas input ports to wire distilled-sampling upstreams such as BasicGuider / ViggleTurboSigmas directly. Steps rule: steps always wins — external sigmas only apply when their step count matches steps; when they mismatch, external sigmas are ignored and regenerated from steps (for a distilled LoRA keep steps equal to the LoRA/sigma sequence length).