feat(planner): persist reusable action semantics

tests/test_world_models.py

@@ -66,12 +66,18 @@ def test_world_event_with_rationale_thinking_page() -> None:
         success=True,
         rationale="Previous step opened settings. Now tapping account.",
         thinking="I should navigate to account settings.",
+        arguments={"x": 12, "y": 34},
+        purpose="Open account settings.",
+        expected_outcome="The account settings page is visible.",
         page="Settings",
     )
     data = event.to_dict()
 
     assert data["rationale"] == "Previous step opened settings. Now tapping account."
     assert data["thinking"] == "I should navigate to account settings."
+    assert data["arguments"] == {"x": 12, "y": 34}
+    assert data["purpose"] == "Open account settings."
+    assert data["expected_outcome"] == "The account settings page is visible."
     assert data["page"] == "Settings"
     assert data["scene_summary"] is None
 
@@ -82,6 +88,9 @@ def test_world_event_all_optional_fields_none() -> None:
 
     assert data["rationale"] is None
     assert data["thinking"] is None
+    assert data["arguments"] == {}
+    assert data["purpose"] is None
+    assert data["expected_outcome"] is None
     assert data["page"] is None
     assert data["scene_summary"] is None
     assert data["action"] == "swipe"