fix(ui2): clear showcmd virt_text together with search count

Problem: when the search count is displayed, the showcmd virt_text is
set to 11 empty spaces to ensure a consistent distance between search
count and ruler, or screen edge in case of noruler. But when the search
count is removed to make place for a message, the empty dummy showcmd
remains and unnecessarily erases part of the message.

Solution: properly remove showcmd together with search count.

runtime/lua/vim/_core/ui2/messages.lua

@@ -462,6 +462,7 @@ function M.msg_show(kind, content, replace_last, _, append, id, trigger)
       M.cmd.last_emsg = (kind == 'emsg' or kind == 'wmsg') and os.time() or M.cmd.last_emsg
       -- Should clear the search count now, mark itself is cleared by invalidate.
       M.virt.last[M.virt.idx.search][1] = nil
+      M.virt.last[M.virt.idx.cmd] = {}
     end
     -- When message was emitted below an already expanded cmdline, move and route to pager.
     tgt = ui.cmd.expand > 0 and 'pager' or tgt

test/functional/ui/messages2_spec.lua

@@ -1092,14 +1092,15 @@ describe('messages2', function()
   end)
 
   it('search count is cleared', function()
-    command('set ruler shortmess-=S | call setline(1, ["foo", "bar"])')
+    command('set ruler showcmd shortmess-=S | call setline(1, ["foo", "bar"])')
     feed('/foo<CR>')
-    screen:expect([[
+    local search_count = [[
       {10:^foo}                                                  |
       bar                                                  |
       {1:~                                                    }|*11
       /foo           W [1/1]             1,1            All|
-    ]])
+    ]]
+    screen:expect(search_count)
     feed('<C-L>j')
     screen:expect([[
       {10:foo}                                                  |
@@ -1107,5 +1108,14 @@ describe('messages2', function()
       {1:~                                                    }|*11
                                          2,1            All|
     ]])
+    feed('n')
+    screen:expect(search_count)
+    command('echo "-"->repeat(&columns)')
+    screen:expect([[
+      {10:^foo}                                                  |
+      bar                                                  |
+      {1:~                                                    }|*11
+      -----------------------------------1,1            All|
+    ]])
   end)
 end)