Add a Properties view for the app root

The root tree row now names the app component, "app (<host:port>)" or
"app (<file>)", and offers Properties from its context menu and on
double-click. The live DOM's <app> element now carries its type and slot
values, and the refresh-by-id lookup finds it, so the view shows real
sys::App values.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

device_session.py

@@ -300,6 +300,10 @@ class DeviceSession:
         app_elem = ET.SubElement(sax_root, "app")
         if root_comp is not None:
             app_elem.set("id", str(root_comp.id))
+            # The app is a component like any other, so the Properties view needs its
+            # type and slot values too. A .sax file leaves both implied; here they are not.
+            app_elem.set("type", root_comp.type_name)
+            self._add_prop_elements(app_elem, root_comp)
             for child_id in root_comp.children:
                 child_comp = self.sox_client.cache_get(child_id)
                 if child_comp is not None:
@@ -318,22 +322,7 @@ class DeviceSession:
             "type": type_qname,
         }
         comp_elem = ET.SubElement(parent_elem, "comp", **attribs)
-
-        slots = self.sox_client.slot_registry.get(
-            (sox_comp.kit_id, sox_comp.type_id))
-        if slots:
-            for slot in slots:
-                if slot.get("is_action"):
-                    continue
-                name = slot["name"]
-                if name in sox_comp.values:
-                    val = sox_comp.values[name]
-                    if isinstance(val, float):
-                        val_str = _fmt_float(val, _slot_precision(type_qname, name))
-                    else:
-                        val_str = str(val)
-                    ET.SubElement(comp_elem, "prop",
-                                  name=name, val=val_str)
+        self._add_prop_elements(comp_elem, sox_comp)
 
         for child_id in sox_comp.children:
             child_comp = self.sox_client.cache_get(child_id)
@@ -346,6 +335,24 @@ class DeviceSession:
 
         return comp_elem
 
+    def _add_prop_elements(self, comp_elem, sox_comp):
+        """Writes a <prop> for every cached non-action slot value of `sox_comp`."""
+        slots = self.sox_client.slot_registry.get(
+            (sox_comp.kit_id, sox_comp.type_id))
+        if not slots:
+            return
+        for slot in slots:
+            if slot.get("is_action"):
+                continue
+            name = slot["name"]
+            if name in sox_comp.values:
+                val = sox_comp.values[name]
+                if isinstance(val, float):
+                    val_str = _fmt_float(val, _slot_precision(sox_comp.type_name, name))
+                else:
+                    val_str = str(val)
+                ET.SubElement(comp_elem, "prop", name=name, val=val_str)
+
     def build_links_elements(self, sax_root):
         """Adds <link> elements under a <links> container, matching .sax structure."""
         links_elem = sax_root.find("links")
@@ -449,6 +456,9 @@ class DeviceSession:
     @staticmethod
     def _find_element_by_id(root, comp_id):
         target = str(comp_id)
+        app_elem = root.find("app")
+        if app_elem is not None and app_elem.get("id") == target:
+            return app_elem
         for elem in root.iter("comp"):
             if elem.get("id") == target:
                 return elem