fix: strip partial think tags in streaming output

nanobot/utils/helpers.py

@@ -32,6 +32,8 @@ def strip_think(text: str) -> str:
          explanatory prose that mentions these tokens.
       5. Orphan closing tags `</think>` / `</thought>` **at the very start
          or end of the text** only, for the same reason.
+      6. Trailing partial control tags split across stream chunks, such as
+         `<thi`, `<thin`, or `<tho`.
 
     Since this is also applied before persisting to history (memory.py),
     the edge-only stripping of (4) and (5) is deliberate: stripping those
@@ -58,6 +60,14 @@ def strip_think(text: str) -> str:
     text = re.sub(r"\s*</thought>\s*$", "", text)
     # Edge-only channel markers (harmony / Gemma 4 variant leaks).
     text = re.sub(r"^\s*<\|?channel\|?>\s*", "", text)
+    # Stream chunks may end in the middle of a control tag. Strip only known
+    # control-token prefixes at the very end.
+    partial_control_tag = (
+        r"</?(?:t|th|thi|thin|think|tho|thou|thoug|though|thought)"
+        r"|<\|?(?:c|ch|cha|chan|chann|channe|channel|channel\|?)"
+    )
+    text = re.sub(rf"(?:{partial_control_tag})$", "", text)
+    text = re.sub(r"^\s*<\|?$", "", text)
     return text.strip()