stellar tx takes input as files and stdin

[janewang]

What would you like to see?

Current stellar tx only takes input as stdin. Like stellar xdr it should also accept files as inputs

Slack discussion here: https://stellarfoundation.slack.com/archives/C06KTGUULUF/p1736212430852659

[sagpatil]

@leighmcculloch fyi

[leighmcculloch]

Recommend having a look at the stellar-xdr cli (that powers the stellar xdr command) for how it does files or stdin in its UI, to see if that same pattern would work for the stellar tx command:

https://github.com/stellar/rs-stellar-xdr/blob/28391e81229ad20a3d9ec56e1e1f382205335085/src/cli/encode.rs#L171-L183

The goal is not just to add the feature, but to maintain a UX parity between the stellar xdr command and the other commands that also work with xdr.