feat: add --haiku flag to format responses as haikus

aider/args.py

@@ -1,6 +1,5 @@
 #!/usr/bin/env python
 
-#ai add --haiku!
 import argparse
 import os
 import sys
@@ -725,6 +724,12 @@ def get_parser(default_config_files, git_root):
         default=True,
         help="Enable/disable fancy input with history and completion (default: True)",
     )
+    group.add_argument(
+        "--haiku",
+        action="store_true",
+        help="Format assistant responses as haikus",
+        default=False,
+    )
 
     ##########
     group = parser.add_argument_group("Voice Settings")