fix(mcphub-nvim): disable make_vars to prevent codecompanion load order error

Closes #1777

make_vars=true triggers variable registration before codecompanion is
fully initialized, causing pairs(nil) crash. Disable by default.

Author: syltharion

lua/astrocommunity/editing-support/mcphub-nvim/init.lua

@@ -16,7 +16,7 @@ return {
             callback = "mcphub.extensions.codecompanion",
             opts = {
               show_result_in_chat = true,
-              make_vars = true,
+              make_vars = false,
               make_slash_commands = true,
             },
           },