fix(provider): restore reasoning_content and extra_content in message sanitization

reasoning_content and extra_content were accidentally dropped from
_ALLOWED_MSG_KEYS.

Also fix session/manager.py to include reasoning_content when building
LLM messages from session history, so the field is not lost across
turns.

Without this fix, providers such as Kimi, emit reasoning_content in
assistant messages will have it stripped on the next request, breaking
multi-turn thinking mode.

Fixes: https://github.com/HKUDS/nanobot/issues/2777
Signed-off-by: Lingao Meng <menglingao@xiaomi.com>

nanobot/providers/openai_compat_provider.py

@@ -21,6 +21,7 @@ if TYPE_CHECKING:
 
 _ALLOWED_MSG_KEYS = frozenset({
     "role", "content", "tool_calls", "tool_call_id", "name",
+    "reasoning_content", "extra_content",
 })
 _ALNUM = string.ascii_letters + string.digits
 

nanobot/session/manager.py

@@ -54,7 +54,7 @@ class Session:
         out: list[dict[str, Any]] = []
         for message in sliced:
             entry: dict[str, Any] = {"role": message["role"], "content": message.get("content", "")}
-            for key in ("tool_calls", "tool_call_id", "name"):
+            for key in ("tool_calls", "tool_call_id", "name", "reasoning_content"):
                 if key in message:
                     entry[key] = message[key]
             out.append(entry)