fix: walk must be array when passed to client

[olizilla]

Ensure the walk param is converted to an array before passing it to the client

sade opts handling:

input	output
--walk foo	{ opts: { walk: 'foo' }}
--walk foo --walk bar	{ opts: { walk: ['foo', 'bar'] }}
--walk foo,bar	{ opts: { walk: 'foo,bar' }

as such we needed to manually split on comma where provided, or upgrade to an array where only a single option was provided.

License: MIT