When forgetting to specify an input file, tippecanoe hangs

It would be useful to get a warning when you forget to specify an input file.
Currently, the code just hangs and does not indicate that you have made a mistake.

Start by tracing tippecanoe's command-line handling when no input file is provided. Reproduce the hang with an invocation that omits the input file, then identify the appropriate warning and verify that the command exits instead of hanging.

Written by the indexing model from the issue text.