Esc and Ctrl+C while a task is running should do the same thing. There
were some cases where pressing Esc would leave a "stuck" widget in the
history; this fixes that and cleans up the logic so there's just one
path for interrupting the task. Also clean up some subtly mishandled key
events (e.g. Ctrl+D would quit the app while an approval modal was
showing if the textarea was empty).
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Co-authored-by: Ahmed Ibrahim <aibrahim@openai.com>