Enable isolated declarations

[wjhsf]

I recently learned about isolated declarations, which enforces some rules on type definitions that make it easier for downstream tooling to get type information without running a full type check. In order to do this, we have to slightly hide our custom inspect function.

I also switched us from importsNotUsedAsValues to verbatimModuleSyntax because the former is deprecated in favor of the latter.

[wjhsf]

Our tooling for API documentation generation doesn't recognize isolatedDeclarations. Since this isn't a priority, I'm going to close for now; we can revisit once the tooling has been updated.