[Codex App] Move projectless chat workspaces out of Documents and make the location configurable

What variant of Codex are you using?

Codex App on macOS

What feature would you like to see?

Please change the default location used for projectless chat workspaces and allow users to configure it.

This request has two parts:

1. Move the default workspace root out of ~/Documents.
2. Allow users to override the default location in the Codex App settings or through a supported configuration option.

Currently, starting a chat without selecting a project automatically creates a generated workspace under:

~/Documents/Codex/YYYY-MM-DD/<chat-directory>

On macOS, ~/Documents is commonly managed by iCloud Drive when Desktop & Documents syncing is enabled. This causes generated projectless-chat workspaces, temporary files, and output files to be synchronized automatically.

Generated application workspaces should not use a commonly synchronized user-document directory by default. Users may not discover the behavior until a significant amount of data has already been uploaded.

A more appropriate platform-specific default could be:

• macOS: ~/Library/Application Support/Codex/Workspaces
• Windows: %LOCALAPPDATA%\Codex\Workspaces
• Linux: $XDG_DATA_HOME/codex/workspaces or ~/.local/share/codex/workspaces

In addition to changing the default, please provide either:

• A setting in the Codex App for selecting the projectless chat workspace root; or
• A supported config.toml option, such as projectless_workspace_root.

Suggested migration behavior:

1. Newly created projectless chats should use the new platform-specific default.
2. Existing chats should continue referencing their original directories.
3. Existing directories should not be moved automatically without user confirmation.
4. Users should be able to choose a custom local directory.
5. The app should validate that the selected directory is writable.
6. The existing work/ and outputs/ directory structure should remain unchanged.

Additional information

Environment:

• Codex App version: 26.818.41509
• Platform: Darwin 25.6.0 arm64 arm
• The macOS Documents directory is managed by the iCloud File Provider

In my case, ~/Documents/Codex has grown to approximately 1.7 GB across roughly 219 generated chat directories, all of which are subject to iCloud synchronization.

Selecting a dedicated project outside Documents is a possible workaround, but it changes the projectless-chat workflow and requires a project to be selected.

Suggested behavior:

1. The setting should apply to newly created projectless chats.
2. Existing chats should continue referencing their original directories.
3. The app should validate that the selected directory is writable.
4. The existing work/ and outputs/ directory structure should remain unchanged.