Show action required in terminal title

[canvrno-oai]

Implements #18162

This updates the TUI terminal title to show an explicit action-required state when Codex is blocked on user approval or input. The terminal title now uses the activity title item to cover both active work and blocked-on-user states, while still accepting the legacy spinner config value.

Changes

• Rename the terminal title item from spinner to activity while preserving legacy config compatibility
• Show [ ! ] Action Required while approval or input overlays are active, with a blinking [ . ] alternate state
• Suppress the normal working spinner while Codex is blocked on user action
• Add targeted coverage for action-required title behavior and legacy title-item parsing

Testing

• Trigger an approval or input modal and confirm the tab title alternates between [ ! ] Action Required and [ . ] Action Required
• Disable the activity title item and confirm the action-required title does not appear
• Resolve the prompt and confirm the title returns to the normal spinning/idel state

Screen.Recording.2026-04-17.at.1.32.08.PM.mov