gtk: add "Close Split" to right-click context menu

Add a "Close Split" option to the split submenu in the right-click
context menu, allowing users to close the focused split pane directly
from the context menu.

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

src/apprt/gtk/class/split_tree.zig

@@ -186,6 +186,7 @@ pub const SplitTree = extern struct {
             .init("new-split", actionNewSplit, s_variant_type),
             .init("equalize", actionEqualize, null),
             .init("zoom", actionZoom, null),
+            .init("close-pane", actionClosePane, null),
         };
 
         _ = ext.actions.addAsGroup(Self, self, "split-tree", &actions);
@@ -663,6 +664,15 @@ pub const SplitTree = extern struct {
         self.as(gobject.Object).notifyByPspec(properties.tree.impl.param_spec);
     }
 
+    pub fn actionClosePane(
+        _: *gio.SimpleAction,
+        _: ?*glib.Variant,
+        self: *Self,
+    ) callconv(.c) void {
+        const surface = self.getActiveSurface() orelse return;
+        surface.close();
+    }
+
     fn surfaceCloseRequest(
         surface: *Surface,
         self: *Self,

src/apprt/gtk/ui/1.2/surface.blp

@@ -316,6 +316,11 @@ menu context_menu_model {
         action: "split-tree.new-split";
         target: "right";
       }
+
+      item {
+        label: _("Close Split");
+        action: "split-tree.close-pane";
+      }
     }
 
     submenu {