[v3] Bug: Piping stdin to `rec` command fails (worked in v2)

Pre-submission checks

• I have searched existing issues and this bug has not been reported yet
• This is a bug report for asciinema CLI (not player or server)

Bug Description

Piping commands to asciinema rec for automation worked perfectly in v2.4.0 but fails in v3.0.1.

Steps to Reproduce

printf "echo hhh\nexit\n" | asciinema rec demo.cast

Expected Behavior

• v2.4.0: Records successfully and exits.
• v3.0.1: Fails.The command hangs not capture the input

Operating System

macOS 24.6.0

asciinema CLI Version

3.0.1

Installation Method

Downloaded binary

Terminal Information

• Shell: zsh 5.9 (arm64-apple-darwin24.0)

Additional Context

No response