perf(ltm): use len(s) instead of len(s.encode()) in trim loop

Avoid allocating a new bytes object for every string when calculating
buffer size in _trim_raw_records. Character count is sufficient for
the approximate memory cap.

Author: RC-CHN

astrbot/builtin_stars/astrbot/long_term_memory.py

@@ -558,10 +558,10 @@ def _trim_raw_records(self, umo: str, max_bytes: int = MAX_RAW_BYTES) -> None:
         self._raw_cursor[umo] = cursor
 
         # 2. 按大小继续从前面淘汰（限制极端情况的总内存）
-        total = sum(len(s.encode()) for s in dq)
+        total = sum(len(s) for s in dq)
         while total > max_bytes and dq:
             removed = dq.popleft()
-            total -= len(removed.encode())
+            total -= len(removed)
             if cursor > 0:
                 cursor -= 1
         self._raw_cursor[umo] = max(0, cursor)