Share target model embed and head weights for nextn (#4033)

python/sglang/srt/speculative/spec_info.py

@@ -5,24 +5,16 @@ class SpeculativeAlgorithm(IntEnum):
     NONE = auto()
     EAGLE = auto()
 
-    # NEXTN spec decoding is for DeepSeek V3/R1
-    # currently it's implemented based on EAGLE
-    NEXTN = auto()
-
     def is_none(self):
         return self == SpeculativeAlgorithm.NONE
 
     def is_eagle(self):
-        return self == SpeculativeAlgorithm.EAGLE or self == SpeculativeAlgorithm.NEXTN
-
-    def is_nextn(self):
-        return self == SpeculativeAlgorithm.NEXTN
+        return self == SpeculativeAlgorithm.EAGLE
 
     @staticmethod
     def from_string(name: str):
         name_map = {
             "EAGLE": SpeculativeAlgorithm.EAGLE,
-            "NEXTN": SpeculativeAlgorithm.NEXTN,
             None: SpeculativeAlgorithm.NONE,
         }
         if name is not None: