fix(diff): default to boring view

doc/cp.txt

@@ -211,7 +211,7 @@ Here's an example configuration with lazy.nvim: >lua
                           ANSI escape codes are stripped for plain text display.
                           Requires vim.g.terminal_color_* to be configured for
                           proper color display.
-        {diff_mode}       (string, default: "git") Diff backend: "none", "vim", or "git".
+        {diff_mode}       (string, default: "none") Diff backend: "none", "vim", or "git".
                           "none" displays plain buffers without highlighting,
                           "vim" uses built-in diff, "git" provides character-level precision.
         {next_test_key}   (string, default: "<c-n>") Key to navigate to next test case.

lua/cp/config.lua

@@ -101,7 +101,7 @@ M.defaults = {
   filename = nil,
   run_panel = {
     ansi = true,
-    diff_mode = 'git',
+    diff_mode = 'none',
     next_test_key = '<c-n>',
     prev_test_key = '<c-p>',
     toggle_diff_key = 't',