fixes the build
more precise types
moves types closer to symbols
normalizes order of template contents: requires, then types, then others
adds dealias and widen
some validation todos
looks like Type.sig is in fact a bad idea

synthetic trees ftl
I'd say Annot.Doc isn't a mod, but rather a source
introduces the scope API

can't say I like it very much, but it's more or less okay, and
something's better than analysis paralysis
sketches @delegate
Scope.syms => Scope.members
kills Scope#Stmt