Update oumi infer to fall back to interactive mode if no input path is specified.

[taenin]

Description

This is a Quality of Life change for the CLI. If the user doesn't specify interactive inference AND doesn't specify an input path, we'll default to interactive inference.

Additionally, we'll always prevent interactive inference if the user specifies an input file. This is in preparation for removing this flag. We should instead use the presence of the input_file as an indicator for whether or not we run interactive inference.

Related issues

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