UX: WebView native-feel + Context-Menu Redesign + Startup-Fix

- Disable text selection (CSS user-select:none) + block browser
  context menu (contextmenu preventDefault) in all panels
- ContextMenu: pill items, accent hover, entrance animation,
  optional title header — controlled via single ContextMenu.css
- EbenenManager + GeschossManager: show layer name as menu title
- startup.py: skip splash on Cmd+N when plugin already loaded
- startup.py: hook NewDocument so display-modes apply to new docs

rhino/panel_base.py

@@ -267,10 +267,12 @@ def _build_inline_template():
         html = f.read().decode("utf-8")
 
     placeholder_script = '<script>' + _MODE_SCRIPT_PLACEHOLDER + '</script>'
+    _no_select = '<style>*{-webkit-user-select:none!important;user-select:none!important;}</style>'
+    _no_ctx    = '<script>document.addEventListener("contextmenu",function(e){e.preventDefault();},true);</script>'
     if "</head>" in html:
-        html = html.replace("</head>", placeholder_script + "</head>")
+        html = html.replace("</head>", placeholder_script + _no_select + _no_ctx + "</head>")
     else:
-        html = placeholder_script + html
+        html = placeholder_script + _no_select + _no_ctx + html
 
     def inline_css(m):
         p = os.path.join(dist_dir, m.group(1).lstrip("./").replace("/", os.sep))
@@ -353,6 +355,15 @@ def attach_webview(panel, bridge, mode):
             wv.ExecuteScript("window.RHINO_MODE=true;")
         except Exception:
             pass
+        try:
+            wv.ExecuteScript(
+                "var _ds=document.createElement('style');"
+                "_ds.textContent='*{-webkit-user-select:none!important;user-select:none!important;}';"
+                "document.head.appendChild(_ds);"
+                "document.addEventListener('contextmenu',function(e){e.preventDefault();},true);"
+            )
+        except Exception:
+            pass
 
     def on_idle(s, e):
         Rhino.RhinoApp.Idle -= on_idle
@@ -440,6 +451,14 @@ def open_satellite_window(mode, params=None, title=None, size=(420, 560),
     def on_loaded(s, e):
         try: wv.ExecuteScript("window.RHINO_MODE=true;")
         except Exception: pass
+        try:
+            wv.ExecuteScript(
+                "var _ds=document.createElement('style');"
+                "_ds.textContent='*{-webkit-user-select:none!important;user-select:none!important;}';"
+                "document.head.appendChild(_ds);"
+                "document.addEventListener('contextmenu',function(e){e.preventDefault();},true);"
+            )
+        except Exception: pass
 
     wv.DocumentTitleChanged += on_title_
     wv.DocumentLoaded       += on_loaded

rhino/startup.py

@@ -23,11 +23,13 @@ if _HERE not in sys.path:
 # Nutzer waehrend Python-Imports + Panel-Registrierung nicht in eine schwarze
 # Rhino-Oberflaeche schaut. Skipt automatisch wenn Launcher seinen eigenen
 # Splash zeigt (Owner-Marker-Check).
-try:
-    import _startup_splash as _splash_first
-    _splash_first.show()
-except Exception as _ex_splash:
-    print("[STARTUP] splash early:", _ex_splash)
+# Skipt auch wenn Plugin bereits in dieser Session geladen ist (z.B. Cmd+N).
+if not sc.sticky.get("_dossier_startup_scheduled"):
+    try:
+        import _startup_splash as _splash_first
+        _splash_first.show()
+    except Exception as _ex_splash:
+        print("[STARTUP] splash early:", _ex_splash)
 
 # DIAGNOSE — welcher Python-Engine laeuft hier wirklich? Einmalig beim Start.
 print("[STARTUP] Python: {}".format(sys.version))
@@ -299,6 +301,10 @@ def _load_all(sender, e):
         Rhino.RhinoDoc.EndOpenDocument += _on_doc_opened
     except Exception as ex:
         print("[STARTUP] EndOpenDocument-Hook:", ex)
+    try:
+        Rhino.RhinoDoc.NewDocument += _on_doc_opened
+    except Exception as ex:
+        print("[STARTUP] NewDocument-Hook:", ex)
     # Projekt-Config bestimmt, welche Module geladen werden. Ohne Config
     # (kein Launcher benutzt, oder Datei nicht da) laedt der Host alles.
     config = _read_project_config()