TUI: strengthen interactive test coverage and terminal edge-case handling

[rmanibus]

Summary

The TUI now has meaningful behavior, but it still depends on terminal-specific runtime paths that need stronger coverage.

Scope

• Add targeted tests for resize during actions
• Add tests for narrow terminal widths and truncation behavior
• Add coverage for action lifecycle edge cases and interrupted actions
• Review whether e2e coverage should exercise more TUI flows
• Raise confidence around patch coverage for the TUI runtime/action path

Why

• Interactive terminal behavior is easy to regress
• This code touches raw mode, redraws, and action orchestration
• Better coverage reduces review and CI surprises

Related: #132, #211, #213