2FA code never arrives during xtool setup on 1.24.0, and no workaround works on iOS 27.2 #407

Description
Following up on #283, which was closed after #349 landed. On xtool 1.24.0 the password login gets past Logging in... and shows the Code: prompt, but no verification code ever arrives on my trusted devices. Signing in to the same Apple ID at account.apple.com sends codes normally.

I can't use the workaround either:

Manual code (#349 fallback): iOS 27.2 has no "Get Verification Code" option under Settings → [name] → Sign-In & Security.
Code from another sign-in: I started a sign-in at account.apple.com while xtool waited at Code:, tapped Allow on my iPhone, and entered that 6-digit code into xtool. xtool rejected it.
So right now there is no way for me to get a code xtool will accept.

Steps to reproduce
xtool setup
Choose 1: Password
Enter Apple ID + password
Logging in... → Code: prompt appears, but no code is delivered
Expected
A 2FA code arrives on a trusted device. If delivery failed, xtool prints the #349 fallback instructions.

Actual
No code arrives, and no error or fallback message is printed. xtool just waits at Code:.

Environment
xtool 1.24.0
Fedora 46, kernel 7.4.0, x86_64 (native Linux, not WSL)
Trusted device: iPhone on iOS 27.2
Advanced Data Protection enabled; trusted devices are used for 2FA
Notes
Same symptom as the Oct 26 comment on #283 (also 1.24.0).
Possibly related to the GSA user agent change in 1.24.0 (#406) or the Omnisette switch in 1.23.0 (#380).
The #349 fallback instructions need updating, or a different method, for iOS versions that no longer offer "Get Verification Code".
Happy to share verbose logs or a network capture. Let me know which flag or env var to use.