Expose GenAI context and prefill lengths in winml build

[Qiong Wu (qiowu) (DingmaomaoBJTU)]

Summary

• add positive-integer --max-cache-len and --prefill-seq-len options to winml build
• forward optional overrides through the architecture-agnostic GenAI bundle dispatch while preserving recipe defaults when omitted
• reject the bundle-only options on generic builds instead of silently ignoring them
• update build and Qwen3 bundle documentation with the one-command workflow
• add focused CLI coverage for defaults, forwarding, validation, and generic-build rejection