"Don't Trust" option blocks all writes instead of requesting approval

What version of Codex is running?

v0.45.0

Which model were you using?

gpt-5-codex

What platform is your computer?

Darwin 23.6.0 arm64

What steps can reproduce the bug?

1. Start Codex in a directory
2. When the trust directory prompt appears, select option 2: "No, ask me to approve edits and commands"
3. Ask Codex to make any file edit, for example: "Update the README.md and add a Hello below the title"

What is the expected behavior?

Codex should ask for approval before making the edit, then proceed with the operation after I approve it.

What do you see instead?

Codex refuses to perform any write operations, saying it's in a "read-only workspace":

• I'm currently in a read-only workspace, so I can't modify README.md.
  If you switch me to a writable mode (or apply the change yourself),
  I'll be happy to add the "Hello" right under the title.

<img width="693" height="1089" alt="Image" src="https://github.com/user-attachments/assets/5016b956-1b16-4be8-ae8b-566b78b49ca8" />

Additional information

This might be related to #2005, which also involved approval prompts and sandbox behavior.

The "Don't Trust" option should enable approval mode, not block all operations entirely.