fix: skip context copy when using placeholder input

aider/coders/base_coder.py

@@ -797,6 +797,7 @@ class Coder:
                 return self.partial_response_content
             while True:
                 try:
+                    if not self.io.placeholder:
                         self.copy_context()
                     user_message = self.get_input()
                     self.run_one(user_message, preproc)