Issue

While passing --chat-mode ask via the command line successfully forces Aider to boot into the ask> prompt, attempting to set this globally using AIDER_CHAT_MODE=ask in a .env file is completely ignored, forcing the application back into default code mode. All other env flags (like AIDER_SHOW_DIFFS) parse correctly. There should be parity between the CLI flags and the .env parameters.

Version and model info

Aider v0.86.2
Model: openai/protected.gpt-4o with diff edit format
Git repo: .git with 1 files
Repo-map: using 1024 tokens, auto refresh