[codex] Fix TUI wrapping for external borrowed slices

[canvrno-oai]

Fixes #20587, reported by @noeljackson.

This prevents the TUI wrapping code from panicking when textwrap returns a borrowed slice that does not point into the original source text. The fix follows the direction proposed by @misrtjakub in the issue comment: validate the borrowed slice pointer range first, and fall back to the existing owned-line mapper when the slice is external.

• Guards borrowed wrapped slices before converting pointer offsets into byte ranges.
• Reuses the existing owned-line range recovery path for external borrowed slices.
• Adds coverage for rejecting borrowed slices outside the source text.

End-user testing steps:

• Start Codex in TUI mode under a PTY wrapper that can inject stdin after startup.
• Inject \x1b[200~test message\x1b[201~\r after the TUI is ready.
• Confirm Codex does not panic and the pasted text is handled normally.

Local validation:

• cargo test -p codex-tui wrapping::tests::
• cargo test -p codex-tui -- --skip status::tests::status_permissions_full_disk_managed_with_network_is_danger_full_access --skip status::tests::status_permissions_full_disk_managed_without_network_is_external_sandbox

[canvrno-oai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. More of your lovely PRs please.

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".