Toolshed (#17895)

* ogh

* i should save my work

* ogh

* hhcdfhjbghshbxdfhghshc
- lots of bugs in parsing still
- invocation is a stub

* expr parsing works

* awawa

* Saving work

* Improve APIs a bit all around, add shortcuts.

* awa

* awa

* AAAAAA

* save work

* Move shit to engine

* lord

* bql is kill

* forgot the fucking bike rack

* bql is kill for real

* pjb will kill me

* aughfhbdj

* adgddf

* gdsgvfvxshngfgh

* b

* hfsjhghj

* a

* tf you mean i have to document it

* follow C# standards

* Assorted cleanup and documentation pass, minor bugfix in ValueRefParser.

* Start porting old commands, remove that pesky prefix in favor of integrating with the shell.

* bw

* Fix valueref up a bit, improve autocomplete for it.

* awa

* fix tests

* git shut up

* Arithmetic commands.

* parse improvements

* Update engine.

---------

Co-authored-by: moonheart08 <moonheart08@users.noreply.github.com>

Content.Server/Administration/Toolshed/MarkedCommand.cs

@@ -0,0 +1,16 @@
+using Content.Shared.Administration;
+using Robust.Shared.Toolshed;
+
+namespace Content.Server.Administration.Toolshed;
+
+[ToolshedCommand, AnyCommand]
+public sealed class MarkedCommand : ToolshedCommand
+{
+    [CommandImplementation]
+    public IEnumerable<EntityUid> Marked([CommandInvocationContext] IInvocationContext ctx)
+    {
+        var res = (IEnumerable<EntityUid>?)ctx.ReadVar("marked");
+        res ??= Array.Empty<EntityUid>();
+        return res;
+    }
+}