feat(tui): shortcuts to change reasoning level temporarily

[fcoury-oai]

Summary

Adds main-chat shortcuts for changing reasoning effort one step at a time:

• Alt+, lowers reasoning (has the < arrow on the key)
• Alt+. raises reasoning (similarly, has the > arrow)

The shortcut updates the active session only. It does not persist the selected reasoning level as the default for future sessions. In Plan mode, it applies temporarily to Plan mode without opening the global-vs-Plan scope prompt.

Details

The shortcut uses the active model preset to decide which reasoning levels are valid. If the current session has no explicit reasoning effort, it starts from the model default. Each keypress moves to the next supported level in the requested direction.

The shortcut only runs from the main chat surface. If a popup or modal is open, input remains owned by that UI.

In Plan mode, the shortcut updates the in-memory Plan reasoning override directly. The model/reasoning picker still keeps the existing scope prompt for explicit picker changes.

Notes

Ctrl-plus and Ctrl-minus were considered, but terminals do not deliver those combinations consistently, so this PR uses Alt shortcuts instead.

If the current effort is unsupported by the selected model, the shortcut skips to the nearest supported level in the requested direction. If there is no valid step, it shows the existing boundary message.

Tests

• cargo test -p codex-tui reasoning_shortcuts
• cargo test -p codex-tui reasoning_effort
• cargo test -p codex-tui reasoning_shortcut
• cargo test -p codex-tui footer_snapshots
• cargo test -p codex-tui
• just fix -p codex-tui
• ./tools/argument-comment-lint/run.py -p codex-tui -- --tests

[chatgpt-codex-connector]

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[canvrno-oai]

Tested and confirmed that alt keys adjust thinking level