agent: use ContextVar for tool routing context

nanobot/agent/tools/cron.py

@@ -58,14 +58,14 @@ class CronTool(Tool):
     def __init__(self, cron_service: CronService, default_timezone: str = "UTC"):
         self._cron = cron_service
         self._default_timezone = default_timezone
-        self._channel = ""
-        self._chat_id = ""
+        self._channel: ContextVar[str] = ContextVar("cron_channel", default="")
+        self._chat_id: ContextVar[str] = ContextVar("cron_chat_id", default="")
         self._in_cron_context: ContextVar[bool] = ContextVar("cron_in_context", default=False)
 
     def set_context(self, channel: str, chat_id: str) -> None:
         """Set the current session context for delivery."""
-        self._channel = channel
-        self._chat_id = chat_id
+        self._channel.set(channel)
+        self._chat_id.set(chat_id)
 
     def set_cron_context(self, active: bool):
         """Mark whether the tool is executing inside a cron job callback."""
@@ -155,7 +155,9 @@ class CronTool(Tool):
                 "describing what to do when the job triggers "
                 "(e.g. the reminder text). Retry including message=\"...\"."
             )
-        if not self._channel or not self._chat_id:
+        channel = self._channel.get()
+        chat_id = self._chat_id.get()
+        if not channel or not chat_id:
             return "Error: no session context (channel/chat_id)"
         if tz and not cron_expr:
             return "Error: tz can only be used with cron_expr"
@@ -194,8 +196,8 @@ class CronTool(Tool):
             schedule=schedule,
             message=message,
             deliver=deliver,
-            channel=self._channel,
-            to=self._chat_id,
+            channel=channel,
+            to=chat_id,
             delete_after_run=delete_after,
         )
         return f"Created job '{job.name}' (id: {job.id})"