feat(tui): make turn interruption keybind configurable

[fcoury-oai]

Why

Interrupting an active turn is currently fixed to Esc, which is easy to hit accidentally and cannot be customized through /keymap. This gives users a less accidental binding while preserving the existing default.

What Changed

• Adds tui.keymap.chat.interrupt_turn to /keymap, defaulting to esc and supporting remapping or unbinding.
• Uses the configured interrupt binding for running-turn status, queued steer interruption, and request_user_input, including the visible hints.
• Preserves local Esc behavior for popups, Vim insert mode, and /agent editing while validating conflicts with fixed/backtrack and request-input navigation bindings.
• Adds behavior and snapshot coverage for remapped interruption paths.

How to Test

1. Run Codex and open /keymap, then set Interrupt Turn to f12.
2. Start a turn and confirm Esc no longer interrupts it while f12 does; the running hint should display f12 to interrupt.
3. Queue a steer while a turn is running and confirm the preview displays f12; pressing it should interrupt and submit the steer immediately.
4. Trigger a request_user_input prompt and confirm its footer uses f12; with notes open, Esc should still clear notes while f12 interrupts the turn.
5. Clear the Interrupt Turn binding and confirm the key-specific interrupt hint is removed while Ctrl+C remains available.

Targeted validation:

• just write-config-schema
• just fix -p codex-config
• just fix -p codex-tui
• just fmt
• just argument-comment-lint-from-source -p codex-config -p codex-tui
• just test -p codex-config
• cargo insta pending-snapshots --manifest-path tui/Cargo.toml
• just test -p codex-tui keymap_setup::tests
• just test -p codex-tui (fails in two pre-existing guardian feature-flag tests unrelated to this diff; the intentional picker snapshot updates were reviewed and accepted)

[etraut-openai]

Code looks good

I built and validated manually