Feature Request: read --json from a file or stdin #229

--json takes the whole input inline, which the README recommends for machine-generated invocations such as an LLM calling the CLI. Linux limits a single argument to 128 KiB, though, so a larger input cannot be passed at all: with a 131,072-byte value the shell fails with "Argument list too long" before the CLI starts. An input that carries file contents is easily that large.

curl's -d handles the same case with a prefix: "If you start the data with the letter @, the rest should be a filename. "@-" makes curl read the data from stdin." gh api -F key=@file works the same way. --json @path and --json @- would cover it without a new option, and cannot be confused with inline JSON, which never starts with @.

We currently rewrite our own --input <file> into --json <contents> before calling run(). Would you accept @path and @- for --json?