fix: vim.schedule QuitPre event callback

so that callback attached by consumer gets
the chance to run first

lua/nui/layout/init.lua

@@ -69,9 +69,9 @@ local function wire_up_layout_components(layout, box)
       autocmd.create({ "BufWipeout", "QuitPre" }, {
         group = layout._.augroup.unmount,
         buffer = child.component.bufnr,
-        callback = function()
+        callback = vim.schedule_wrap(function()
           layout:unmount()
-        end,
+        end),
       }, child.component.bufnr)
 
       autocmd.create("BufWinEnter", {

lua/nui/popup/init.lua

@@ -187,9 +187,9 @@ function Popup:mount()
   autocmd.create("QuitPre", {
     group = self._.augroup.unmount,
     buffer = self.bufnr,
-    callback = function()
+    callback = vim.schedule_wrap(function()
       self:unmount()
-    end,
+    end),
   }, self.bufnr)
   autocmd.create("BufWinEnter", {
     group = self._.augroup.unmount,

lua/nui/split/init.lua

@@ -186,8 +186,10 @@ function Split:mount()
     buffer = self.bufnr,
     callback = function()
       self._.pending_quit = true
-      self:unmount()
-      self._.pending_quit = nil
+      vim.schedule(function()
+        self:unmount()
+        self._.pending_quit = nil
+      end)
     end,
   }, self.bufnr)
   autocmd.create("BufWinEnter", {

tests/nui/layout/init_spec.lua

@@ -522,6 +522,10 @@ describe("nui.layout", function()
 
         p2:unmount()
 
+        vim.wait(100, function()
+          return not layout._.mounted
+        end, 10)
+
         assert.spy(layout_unmount).was_called()
       end)
 
@@ -547,6 +551,10 @@ describe("nui.layout", function()
           vim.cmd([[quit]])
         end)
 
+        vim.wait(100, function()
+          return not layout._.mounted
+        end, 10)
+
         assert.spy(layout_unmount).was_called()
       end)
     end)
@@ -1479,6 +1487,10 @@ describe("nui.layout", function()
 
         s2:unmount()
 
+        vim.wait(100, function()
+          return not layout._.mounted
+        end, 10)
+
         assert.spy(layout_unmount).was_called()
       end)
 
@@ -1509,6 +1521,10 @@ describe("nui.layout", function()
           vim.cmd([[quit]])
         end)
 
+        vim.wait(100, function()
+          return not layout._.mounted
+        end, 10)
+
         assert.spy(layout_unmount).was_called()
       end)
     end)