Add --auto-accept-architect feature

Commentary

• 0:01 We're going to add a new feature to automatically accept edits proposed by the architect model.
• 0:11 First, let's add the new switch.
• 0:40 Aider figured out that it should be passed to the Coder class.
• 0:48 Now we need to implement the functionality.
• 1:00 Let's do some manual testing.
• 1:28 That worked. Let's make sure we can turn it off too.
• 1:42 That worked too. Let's have aider update the HISTORY file to document the new feature.
• 2:00 Let's quickly tidy up the changes to HISTORY.
• 2:05 All done!