fix(cli): rebind interactive stdin to controlling tty

[huangsen365]

Summary

• Detect when interactive CLI stdin is not usable by prompt_toolkit (non-TTY or selector registration failure)
• Rebind fd 0 to /dev/tty for interactive mode so macOS/kqueue does not crash with OSError: [Errno 22] Invalid argument
• Add regression tests for non-TTY stdin, selector EINVAL, and /dev/tty rebinding

Root cause

When Hermes is launched from a piped installer/wrapper, fd 0 can remain connected to the pipe instead of the controlling terminal. The previous guard only checked os.fstat(0), so prompt_toolkit still attempted loop.add_reader(0, ...) and macOS kqueue could raise OSError(EINVAL). Linux tolerates this path more often, which is why the crash appeared macOS-specific.

Test Plan

• scripts/run_tests.sh tests/cli/test_interactive_stdin.py -q
• scripts/run_tests.sh tests/cli/ -q

[teknium1]

Closing — superseded by #26077 (merged as commit d3d5916), which preventively probes kqueue at startup and falls back to SelectSelector when fd 0 cannot be registered. The widened except-clause matching EINVAL / EBADF / 'Invalid argument' — which most PRs in this cluster including yours added — is also included.

Thanks for the fix; closing as duplicate of the merged work.