fix: correct import path for build_routing_context in executor (#214)

routing.types appears to have been an in-progress module that was
consolidated into routing.router before it was created. The lazy
import inside the router policy block was silently caught by the
surrounding try/except, causing the policy to never activate and
the executor to always fall back to the configured model regardless
of any router_policy setting.

Corrects the import to openjarvis.learning.routing.router where
build_routing_context is defined and exported.

src/openjarvis/agents/executor.py

@@ -261,7 +261,7 @@ class AgentExecutor:
         if router_policy_key and self._system:
             try:
                 from openjarvis.core.registry import RouterPolicyRegistry
-                from openjarvis.learning.routing.types import (
+                from openjarvis.learning.routing.router import (
                     build_routing_context,
                 )