Fix: prio synonym match than wordnet for english (#10762)

### What problem does this PR solve?

Fix: prio synonym match than wordnet for english

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

rag/nlp/synonym.py

@@ -32,6 +32,7 @@ class Dealer:
         path = os.path.join(get_project_base_directory(), "rag/res", "synonym.json")
         try:
             self.dictionary = json.load(open(path, 'r'))
+            self.dictionary = { (k.lower() if isinstance(k, str) else k): v for k, v in self.dictionary.items() }
         except Exception:
             logging.warning("Missing synonym.json")
             self.dictionary = {}
@@ -66,18 +67,34 @@ class Dealer:
         except Exception as e:
             logging.error("Fail to load synonym!" + str(e))
 
-    def lookup(self, tk, topn=8):
-        if re.match(r"[a-z]+$", tk):
-            res = list(set([re.sub("_", " ", syn.name().split(".")[0]) for syn in wordnet.synsets(tk)]) - set([tk]))
-            return [t for t in res if t]
 
+    def lookup(self, tk, topn=8):
+        if not tk or not isinstance(tk, str):
+            return []
+
+        # 1) Check the custom dictionary first (both keys and tk are already lowercase)
         self.lookup_num += 1
         self.load()
-        res = self.dictionary.get(re.sub(r"[ \t]+", " ", tk.lower()), [])
+        key = re.sub(r"[ \t]+", " ", tk.strip())
+        res = self.dictionary.get(key, [])
         if isinstance(res, str):
             res = [res]
-        return res[:topn]
+        if res:  # Found in dictionary → return directly
+            return res[:topn]
 
+        # 2) If not found and tk is purely alphabetical → fallback to WordNet
+        if re.fullmatch(r"[a-z]+", tk):
+            wn_set = {
+                re.sub("_", " ", syn.name().split(".")[0])
+                for syn in wordnet.synsets(tk)
+            }
+            wn_set.discard(tk)  # Remove the original token itself
+            wn_res = [t for t in wn_set if t]
+            return wn_res[:topn]
+
+        # 3) Nothing found in either source
+        return []
+    
 
 if __name__ == '__main__':
     dl = Dealer()