replace stdin with unsatisfied inputs in root

[andrewdavidmackenzie]

If a flow is compiled/run, then the flow resolved/specified to flowc is considered the root.
If it has unsatisfied inputs, then read them from stdin, in the order defined, using "name" as the prompt.

Maybe chose between string or json input depending on the declared type?
(absence of a specific type being 'json')

e.g. then mandlebrot/generate_pixels.toml could be used directly as part of debug.
flowc mandlebrot/generate_pixels.toml will compile and run it, prompting for the missing stdin lines

unconnected outputs will be printed out to stdout, using "name" as a prefix to show what is being output

[andrewdavidmackenzie]

Prompt with the name of the input that is unsatisfied?
Maybe the route of the IO that is unsatisfied as the prompt?