fix(ci): add stderr to test field, use text=false on vim.system

lua/cp/test.lua

@@ -7,6 +7,7 @@
 ---@field actual_highlights table[]?
 ---@field time_ms number?
 ---@field error string?
+---@field stderr string?
 ---@field selected boolean
 ---@field code number?
 ---@field ok boolean?

spec/execute_spec.lua

@@ -196,7 +196,7 @@ describe('cp.execute', function()
     it('handles command execution', function()
       vim.system = function(_, opts)
         if opts then
-          assert.equals(true, opts.text)
+          assert.equals(false, opts.text)
         end
         return {
           wait = function()