fix stdin hang

[alxnddr]

Closes https://linear.app/metabase/issue/GHY-3714/cli-hangs-on-stdin-input

Description

Fixes the hang when stdin is a pipe that never sends data or EOF (happens when CLI is run from another process like Claude Code), now it waits only short time for first byte and then gives an input required error

[linear]

GHY-3714 CLI hangs on stdin input

mb transform create hangs when invoked with --stdin.

This happened while trying to create transforms in bulk.

The thread notes that --stdin is not a documented flag for this command and that only --body and --file exist. The command likely waited on stdin or rejected the flag silently, and no transforms were created on the server.

Review in Linear