When instantiating a class that uses generics, TypeScript will try to

infer a more specific type for the generics based on the arguments

provided to the constructor.
This can be useful (it's nice to have the proper HTMLElement subclass

for BaseView.el, for example), but it's a problem for model attributes

and for options, because those are usually provided as subset of all

available options.
As an example of where that breaks, if you define an interface of

available attributes for a model, and then instantiate the model with

constructor arguments providing only a subset of those attributes,

TypeScript will consider any other attributes in the interface to be

invalid.
The solution to this is to tell TypeScript not to infer more specific

types for attribute and option arguments. TypeScript 5.4 introduces a

handy NoInfer<T> type for this, but this is also simple enough to

backport into our types, retaining wider compatibility.
We now have type preservation for model attributes and

model/view/router/collection options, while allowing model and DOM

element attributes to be inferred.

Unit tests pass.
Verified this fixed instantiating a model with a subset of attributes

and then trying to access a default attribute.