[codex] Add tmux-aware OSC 9 notifications

[caseychow-oai]

Summary

• wrap OSC 9 notifications in tmux's DCS passthrough so terminal notifications make it through tmux
• use codex-terminal-detection for OSC 9 auto-selection so tmux sessions inherit the underlying client terminal support
• add focused notification backend tests for plain OSC 9 and tmux-wrapped output

Stack

• base PR: test(tui): align memory settings test sqlite home #18479
• review order: test(tui): align memory settings test sqlite home #18479, then this PR

Why

Tmux does not forward OSC 9 notifications directly; the sequence has to be wrapped in tmux's DCS passthrough envelope. Codex also had local notification heuristics that could miss supported terminals when running under tmux, even though codex-terminal-detection already knows how to attribute tmux sessions to the client terminal.

Validation

• just fmt
• cargo test -p codex-tui (currently blocked by an unrelated existing compile error in app-server/src/message_processor.rs:754 referencing connection_id out of scope; not caused by this change)

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 9938ca0a1c

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[fcoury-oai]

Code overall looks good. The only thing is we might have a regression for WezTerm where I pointed it out. Can you add a test to check and fix it if found to be the case?

[fcoury-oai]

I also tested it with Ghostty and tmux and it worked even without the set -g allow-passthrough on and focus-events on. I just had to set focus elsewhere :-)

[fcoury-oai]

Question: did you changes introduce the error you are fixing on the base PR?

The code looks good and I was able to replicate the behavior. I don't think you should submit this PR stacked on the other test fix. I would like to approve this PR with the test error and handle the other one separately. Would that be possible?

[caseychow-oai]

Question: did you changes introduce the error you are fixing on the base PR?

The code looks good and I was able to replicate the behavior. I don't think you should submit this PR stacked on the other test fix. I would like to approve this PR with the test error and handle the other one separately. Would that be possible?

I'll restack and we can see!

[caseychow-oai]

Question: did you changes introduce the error you are fixing on the base PR?

The code looks good and I was able to replicate the behavior. I don't think you should submit this PR stacked on the other test fix. I would like to approve this PR with the test error and handle the other one separately. Would that be possible?

@fcoury-oai looks like this is all green now.

[fcoury-oai]

Great work, can't wait for this to land on an alpha version.

Code looks good, tested and still works.