fix: restore refresh operations broken by nav_gen regression (C-1, S-2)

Change nav_gen default from 0 to None in _fetch_list_contents_bg and
_finalize_list_loading. The guard is updated to only apply when a gen
is explicitly provided (`nav_gen is not None`).

Refresh call sites (lines 1515, 1529, 1538) pass no gen, so they receive
None and bypass the guard — their results are always applied. Navigation
calls still pass an explicit integer gen, so stale-navigation protection
remains fully intact.

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

sharepoint_browser.py

@@ -671,6 +671,7 @@ class SharePointApp(wx.Frame):
         self.current_items = [] # Gemmer graf-objekterne for rækkerne
         self.tree_item_data = {} # Mappenoder -> {type, id, name, drive_id, path}
         self.current_path_data = [] # Gemmer data-objekterne for den nuværende sti (brødkrummer)
+        self._nav_gen = 0  # Incremented on each navigation to discard stale fetch results
         self.tree_root = None
         self.is_navigating_back = False
         self.active_edits = {} # item_id -> { "name": name, "event": Event, "waiting": bool }
@@ -1722,7 +1723,6 @@ class SharePointApp(wx.Frame):
                 all_sites.extend(data.get('value', []))
                 url = data.get('@odata.nextLink')
                 self.set_status(f"{self.get_txt('status_fetching_sites')} ({len(all_sites)}...)")
-                self.pulse_gauge(True)
             else:
                 break
         
@@ -1788,7 +1788,6 @@ class SharePointApp(wx.Frame):
                 res_data = res.json()
                 all_children.extend(res_data.get('value', []))
                 url = res_data.get('@odata.nextLink')
-                self.pulse_gauge(True)
             else:
                 break
         
@@ -1856,8 +1855,8 @@ class SharePointApp(wx.Frame):
 
     def _navigate_to_item_data(self, data, tree_item=None, is_breadcrumb=False):
         try:
-            # Race-condition beskyttelse: Hvis vi allerede er der, så stop (undtagen ved brødkrumme-klik)
-            if not is_breadcrumb and getattr(self, 'current_path', None) == data.get("path"):
+            # Race-condition beskyttelse: Hvis vi allerede er der, så stop
+            if getattr(self, 'current_path', None) == data.get("path"):
                 return
                 
             self.current_path = data["path"]
@@ -1886,12 +1885,14 @@ class SharePointApp(wx.Frame):
             self.list_ctrl.DeleteAllItems()
             self.current_items = []
             self.set_status(self.get_txt("status_loading_content"))
-            
-            threading.Thread(target=self._fetch_list_contents_bg, args=(data,), daemon=True).start()
+
+            self._nav_gen += 1
+            gen = self._nav_gen
+            threading.Thread(target=self._fetch_list_contents_bg, args=(data, gen), daemon=True).start()
         except RuntimeError:
             pass
 
-    def _fetch_list_contents_bg(self, data):
+    def _fetch_list_contents_bg(self, data, nav_gen=None):
         if not self.ensure_valid_token(): return
         self.pulse_gauge(True)
         items_data = []
@@ -1938,8 +1939,7 @@ class SharePointApp(wx.Frame):
             
             items_data.extend(chunk_data)
             self.set_status(self.get_txt("status_loading_items").format(count=len(items_data)))
-            self.pulse_gauge(True)
-            
+
             # Chunked UI Update
             if first_chunk:
                 wx.CallAfter(self._populate_list_ctrl, chunk_data, data, finalize=False)
@@ -1950,7 +1950,7 @@ class SharePointApp(wx.Frame):
             url = res_data.get('@odata.nextLink')
 
         # Finalize
-        wx.CallAfter(self._finalize_list_loading, items_data)
+        wx.CallAfter(self._finalize_list_loading, items_data, nav_gen)
         self.pulse_gauge(False)
 
     def _append_list_items(self, items):
@@ -1973,8 +1973,10 @@ class SharePointApp(wx.Frame):
             self.list_ctrl.SetItem(idx, 2, size_str)
             self.list_ctrl.SetItem(idx, 3, item['modified'])
 
-    def _finalize_list_loading(self, items_data):
+    def _finalize_list_loading(self, items_data, nav_gen=None):
         if not self: return
+        if nav_gen is not None and nav_gen != self._nav_gen:
+            return  # User navigated away; discard stale results
         self.current_items = items_data
         self.apply_sorting()
         self.set_status(self.get_txt("status_ready"))