[Spec] Support MegaMoE for DSpark under dp attention (#34844)

Co-authored-by: weireweire <20922698+weireweire@users.noreply.github.com>

python/sglang/srt/arg_groups/speculative_hook.py

@@ -286,11 +286,24 @@ def _handle_dspark(server_args: ServerArgs) -> None:
     if server_args.enable_dp_attention and server_args.dp_size > 1:
         if not server_args.enable_dp_lm_head:
             raise ValueError("DSpark with dp attention requires --enable-dp-lm-head.")
-        if not _is_npu and server_args.moe_a2a_backend != "none":
+        if not _is_npu and server_args.moe_a2a_backend not in ("none", "megamoe"):
             raise ValueError(
-                "DSpark with dp attention only supports the built-in TP MoE "
-                f"(moe_a2a_backend='none'), got {server_args.moe_a2a_backend!r}."
+                "DSpark with dp attention supports moe_a2a_backend 'none' "
+                "(built-in TP MoE) or 'megamoe', got "
+                f"{server_args.moe_a2a_backend!r}."
             )
+        if not _is_npu and server_args.moe_a2a_backend != "none":
+            from sglang.srt.speculative.ragged_verify import (
+                RaggedVerifyMode,
+                read_ragged_verify_mode,
+            )
+
+            if read_ragged_verify_mode() is not RaggedVerifyMode.STATIC:
+                raise ValueError(
+                    "DSpark with dp attention + "
+                    f"moe_a2a_backend={server_args.moe_a2a_backend!r} requires "
+                    "SGLANG_RAGGED_VERIFY_MODE=static."
+                )
         if server_args.attn_cp_size > 1:
             raise ValueError(
                 "DSpark with dp attention does not support context parallel "