improve stringification of metatable types

[nnullcolumn]

• closes make metatable type stringification friendlier #2544
• changes { @metatable { }, { } } to setmetatable<{ }, { }>
• i updated and ran tests on NixOS 26.05 x86_64 w/ make test
• although this could possibly be conflated w an unsolved built-in type function i think the mental model here should be the same
• this (very small) change is 100% human written

[nnullcolumn]

also, if any dedicated testing or flagging is needed please let me know. i'm hoping i don't need to?