[docs] Add DFlash2 speculative cells to the Qwen3.8-27B cookbook (#35663)

docs/src/snippets/configs/Qwen/qwen3.8-27b.jsx

@@ -116,6 +116,49 @@ export const config = {
               : []),
           ],
         },
+        {
+          id: "dflash", label: "DFLASH2",
+          // Trained block-diffusion draft, a separate checkpoint. The
+          // selector projects through the target lm_head — including
+          // quantized heads — so it runs on the NVFP4 checkpoint too.
+          // Validated on the SM120 pair (NVFP4 measured end to end; the
+          // RTX PRO 6000 BF16/FP8 cells boot-and-serve). On the other
+          // platforms the pick is offered with the in-progress hint below
+          // — the recipe composes from validated cells but has not been
+          // exercised there yet.
+          disabled: (sel) => sel.hw === "rtx5090" && sel.quant !== "nvfp4",
+          disableReason:
+            "On the 32GB RTX 5090 the DFlash2 draft model only fits on top of the NVFP4 weights",
+          hints: (sel) =>
+            ["rtx6000", "rtx5090"].includes(sel.hw)
+              ? []
+              : ["DFLASH2 on this platform: final verification in progress"],
+          // 5090: mem-fraction re-pins like DSPARK's, and fp32 additionally
+          // re-pins the ratio — the balanced L=9216 value leaves the state
+          // pool one slot short at every serviceable mem-fraction (see the
+          // DFlash2 bullet in Configuration Tips).
+          stripPrefixes: (sel) =>
+            sel.hw === "rtx5090"
+              ? sel.ssmDtype === "float32"
+                ? ["--mem-fraction-static", "--mamba-full-memory-ratio"]
+                : ["--mem-fraction-static"]
+              : [],
+          flags: (sel) => [
+            "--speculative-algorithm DFLASH",
+            "--speculative-draft-model-path incoai/Qwen3.8-27B-DFlash2",
+            "--speculative-num-draft-tokens 8",
+            // Measured on the 5090: bf16 state serves at 0.90 (DSPARK's
+            // pin); fp32 fits only at 0.945 + ratio 10 (0.94 is one state
+            // slot short, 0.95 OOMs at runtime) and leaves the Low-Latency
+            // KV pool a single-request envelope.
+            ...(sel.hw === "rtx5090"
+              ? sel.ssmDtype === "float32"
+                ? ["--mem-fraction-static 0.945",
+                   "--mamba-full-memory-ratio 10"]
+                : ["--mem-fraction-static 0.90"]
+              : []),
+          ],
+        },
       ],
     },
     {
@@ -260,6 +303,11 @@ export const config = {
           flags: ["--speculative-algorithm DSPARK",
                   "--speculative-draft-model-path RadixArk/Qwen3.8-27B-DSpark",
                   "--speculative-draft-attention-backend flashinfer"] },
+        { id: "dflash",  label: "DFlash2",
+          // Same trio as the Deploy panel's DFLASH2 option.
+          flags: ["--speculative-algorithm DFLASH",
+                  "--speculative-draft-model-path incoai/Qwen3.8-27B-DFlash2",
+                  "--speculative-num-draft-tokens 8"] },
       ],
     },