File the Fleet nav item under Assets and store policy JSON as TEXT

plugins/endpoints/plugin.py

@@ -177,8 +177,11 @@ class EndpointsPlugin(BasePlugin):
     def get_navigation_items(self) -> List[Dict]:
         """Sidebar entry for the fleet list view.
 
-        Sits just after the PCs item (position 15) because the fleet view is
-        a telemetry lens over the same computers.
+        Filed under Assets, immediately after PCs (position 15), because the
+        fleet view is a telemetry lens over the same computers rather than a
+        different kind of thing. It shipped declaring a section of its own,
+        which rendered a one-item 'Fleet' group at the bottom of the sidebar,
+        far from the PCs it describes.
         """
         return [
             {
@@ -187,7 +190,7 @@ class EndpointsPlugin(BasePlugin):
                 'route': '/endpoints',
                 'position': 16,
                 'permission': 'endpoints.view',
-                'section': 'fleet',
+                'section': 'assets',
             },
         ]