* specials: comment all parser cases
* specials: scan_graph: early-return if args is null
* specials: fix logic in scan_graph
* tests: add scan_graph parsing test
* specials: separate command parsing from graph parsing
this simplifies the implementation of graph parsing and makes it less ambiguous to parse graphs in contexts where commands are not expected
* specials: tweak comments in scan_graph
* tests: update for scan_command separation
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Co-authored-by: bi4k8 <bi4k8@github>
