fix: scope marker reconcile to the current bridge/NIO

The reconcile pass in _ubridge_apply_markers walked the node-wide
_marker_filter_bridges map but compared against `desired`, which only
carries the markers of the NIO being updated. Updating any one link
therefore deleted every other link's markers (and their pcaps) on that
node — a regression from the add-only→reconcile switch. IOU's override
had the same flaw across its ports.

Guard the delete pass with the current bridge (base_node) / IOL location
(IOU) so only markers on the NIO being reconciled can be removed. Added
a regression test that fails without the guard.

gns3server/compute/base_node.py

@@ -1256,7 +1256,13 @@ class BaseNode:
         desired = {(name, spec.get("link_id", "")): spec for name, spec in markers.items()}
 
         # 1. Remove installed markers that are no longer desired (marker/def delete).
+        # Scope to THIS bridge: the map is node-wide and also holds markers
+        # installed on this node's other links/NIOs. Without this guard,
+        # reconciling one NIO would delete every other link's markers + pcaps
+        # (desired only carries the current NIO's markers) — a regression.
         for key in list(self._marker_filter_bridges):
+            if self._marker_filter_bridges[key] != bridge_name:
+                continue
             if key not in desired:
                 mname, link_id = key
                 installed_bridge = self._marker_filter_bridges.pop(key)

gns3server/compute/iou/iou_vm.py

@@ -1291,7 +1291,12 @@ class IOUVM(BaseNode):
         desired = {(name, spec.get("link_id", "")): spec for name, spec in markers.items()}
 
         # 1. Remove installed markers that are no longer desired.
+        # Scope to THIS port's IOL location — the map is node-wide and also
+        # holds markers on this IOU's other ports, which must not be deleted
+        # when reconciling a single NIO (see base_node for the same guard).
         for key in list(self._marker_filter_bridges):
+            if self._marker_filter_bridges[key] != location:
+                continue
             if key not in desired:
                 mname, link_id = key
                 installed_location = self._marker_filter_bridges.pop(key)