fix(quick_chat): remove duplicated instructions

Author: sudo-tee

lua/opencode/quick_chat.lua

@@ -307,7 +307,6 @@ end
 local create_message = Promise.async(function(message, buf, range, context_instance, options)
   local quick_chat_config = config.quick_chat or {}
 
-  -- Generate instructions (allow user override)
   local instructions
   if quick_chat_config.instructions then
     instructions = quick_chat_config.instructions
@@ -323,12 +322,12 @@ local create_message = Promise.async(function(message, buf, range, context_insta
   local result = context.format_message_plain_text(message, context_instance, format_opts):await()
 
   local parts = {
-    { type = 'text', text = instructions_text },
+    { type = 'text', text = table.concat(instructions, '\n') },
     { type = 'text', text = '\n\n' .. string.rep('=', 80) .. '\n\n' .. '# USER REQUEST\n\n' .. result.text },
   }
 
   -- Use instructions as system prompt for models that support it
-  local params = { parts = parts, system = instructions_text }
+  local params = { parts = parts }
 
   local current_model = core.initialize_current_model():await()
   local target_model = options.model or quick_chat_config.default_model or current_model