fix: .pypanel must be XML, not JSON (Houdini convention)

python_panels/hermes_bridge.pypanel

@@ -1,6 +1,34 @@
-{
-    "interface": "hermes_bridge_panel.show",
-    "label": "Hermes Bridge",
-    "icon": "MISC_python",
-    "help_url": "https://git.niklashmotion.art/Hermes/hermes-houdini-bridge"
-}
+<?xml version="1.0" encoding="UTF-8"?>
+<pythonPanelDocument>
+  <interface name="hermes_bridge" label="Hermes Bridge" icon="MISC_python"
+             help_url="https://git.niklashmotion.art/Hermes/hermes-houdini-bridge">
+    <script><![CDATA[
+import sys, os
+
+# Ensure our package scripts are importable
+_pkg = os.environ.get("HHB_PACKAGE", "")
+if _pkg:
+    _scripts = os.path.join(_pkg, "scripts", "python")
+    if _scripts not in sys.path:
+        sys.path.insert(0, _scripts)
+
+from hermes_bridge_panel import HermesBridgePanel
+
+_the_panel = None
+
+def onCreateInterface():
+    global _the_panel
+    _the_panel = HermesBridgePanel()
+    return _the_panel
+
+def onActivateInterface():
+    if _the_panel:
+        _the_panel._refresh_status()
+
+def onDestroyInterface():
+    global _the_panel
+    _the_panel = None
+]]></script>
+    <includeInToolbarMenu menu_position="500" create_separator="true"/>
+  </interface>
+</pythonPanelDocument>