fix(markdown): a rewritten assistant reply reseeds the session instead of resuming it

src/beaver_gateway/frontends/markdown/frontend.py

@@ -400,7 +400,7 @@ class MarkdownFrontend(Frontend):
             messages=outcome.messages,
             origin="user",
             capture=capture,
-            use_session=outcome.divergence_index is None,
+            use_session=outcome.reuse_session,
         )
         try:
             message = await self._stream_to_file(
@@ -623,7 +623,7 @@ class MarkdownFrontend(Frontend):
             messages=outcome.messages,
             origin="user",
             capture=capture,
-            use_session=outcome.divergence_index is None,
+            use_session=outcome.reuse_session,
         )
 
         acc = StreamAccumulator()