Fix live wiresheet links and DOM structure to match .sax format

- Build root children directly under <app> instead of wrapping them in
  a <comp name="app"> element. This matches the .sax DOM structure
  where <app> is the container, so component paths like /AHU/TmpCont/X
  match between link references and get_component_path.

- Fix _comp_path to produce /AHU/TmpCont/X format (skip root id 0,
  leading /) matching the .sax link path convention.

- Format float property values to 4 decimal places instead of full
  Python float precision (22.0116 vs 22.011558532714844).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

device_session.py

@@ -237,7 +237,15 @@ class DeviceSession:
 
         app_elem = ET.SubElement(sax_root, "app")
         if root_comp is not None:
-            self._build_comp_element(app_elem, root_comp)
+            # Build children of root directly under <app>, matching .sax format
+            # where <app> IS the root container (not a <comp>)
+            for child_id in root_comp.children:
+                child_comp = self.sox_client.cache_get(child_id)
+                if child_comp is not None:
+                    self._build_comp_element(app_elem, child_comp)
+                else:
+                    ET.SubElement(app_elem, "comp",
+                                  name="...", id=str(child_id), type="")
 
         return sax_root
 
@@ -259,8 +267,12 @@ class DeviceSession:
                 name = slot["name"]
                 if name in sox_comp.values:
                     val = sox_comp.values[name]
+                    if isinstance(val, float):
+                        val_str = f"{val:.4f}".rstrip("0").rstrip(".")
+                    else:
+                        val_str = str(val)
                     ET.SubElement(comp_elem, "prop",
-                                  name=name, val=str(val))
+                                  name=name, val=val_str)
 
         for child_id in sox_comp.children:
             child_comp = self.sox_client.cache_get(child_id)
@@ -330,7 +342,7 @@ class DeviceSession:
         if not parts:
             return None
         parts.reverse()
-        return "/".join(parts)
+        return "/" + "/".join(parts)
 
     # ── Update DOM from COV ─────────────────────────────────────