[diffusion] doc: fix diffusion docs and cookbook drift (#29302)

docs_new/docs/sglang-diffusion/api/cli.mdx

@@ -83,6 +83,7 @@ Use `sglang generate --help` and `sglang serve --help` for the full argument lis
 - `--sp-degree {N}`: sequence parallelism size
 - `--ulysses-degree {N}` and `--ring-degree {N}`: USP parallelism controls
 - `--enable-cfg-parallel {true|false}`: enable or explicitly disable CFG parallelism
+- `--warmup-mode {off|request|server}`: control startup warmup for `sglang serve`; `off` skips warmup, `request` primes the request path, and `server` runs a full synthetic server warmup before serving traffic
 - `--attention-backend {BACKEND}`: attention backend for native SGLang and diffusers pipelines
 - `--component-attention-backends {MAP}`: per-component attention backend overrides, for example `text_encoder=torch_sdpa,transformer=fa`
 - `--attention-backend-config {CONFIG}`: attention backend configuration