feat: Adds optional read-only response to confirm_ask

[FinnBorge]

As proposed in #3928

This changes the existing confirm_ask prompt from:
Add file to the chat? (Y)es/(N)o/(D)on't ask again [Yes]:
To
Add file to the chat? (Y)es/(N)o/(R)ead-only/(D)on't ask again [Yes]:

It also lays the groundwork for the extension of the confirm_ask method to accept conditional/other responses in various contexts through the use of the string response type. This does produce a touch of code sprawl as there's a need to test for whether the return_string parameter is set in certain situations. Very open to feedback about how best to implement this.

The key points of the implementation are:

1. Added show_readonly parameter to the confirm_ask method in aider/io.py to control when the "Read-only" option appears
2. Added return_string parameter to control the return type
3. Maintained default boolean return values for existing code (through use of the above)
4. Updated check_for_file_mentions to use the new string return values

The implementation ensures that:

• Existing code continues to work without changes
• New file addition prompts can include a "Read-only" option
• The code can handle both boolean and string return values

Also note that this PR includes an unrelated edit that was flagged by the commit hook. This import is not used and caused the commit hook to fail.
-451,8 @@ def test_tool_output_color_handling(self): from rich.text import Text

Please do not hesitate to provide critical feedback!

Warm regards,
Finn

[CLAassistant]

All committers have signed the CLA.

[ocontant]

I like the feature, it add clarity make the tool more intuitive.

[zephschafer]

🔥

[jmarkmorris]

I was late to the party, but I thought of this feature too.