Use NoInfer utility type where applicable

[whatfontisthis]

Summary

Addresses #848 by applying TypeScript 5.4's NoInfer utility type where it genuinely improves inference behavior.

Changes

GetTagMetadata in source/tagged.d.ts

Before:

export type GetTagMetadata<Type extends Tag<TagName, unknown>, TagName extends PropertyKey> = ...

After:

export type GetTagMetadata<Type extends Tag<NoInfer<TagName>, unknown>, TagName extends PropertyKey> = ...

Why NoInfer helps here:

The constraint Type extends Tag<TagName, unknown> creates two potential inference sites for TagName:

1. The structural shape of Type — since Type must extend Tag<TagName, unknown>, TypeScript can infer TagName by inspecting which tags Type carries.
2. The explicit TagName argument itself.

When GetTagMetadata is used in a generic function that accepts both a tagged value and a tag name:

declare function readTag<T extends Tag<K, unknown>, K extends PropertyKey>(
  tagged: T,
  tagName: K
): GetTagMetadata<T, K>;

Without NoInfer, TypeScript may use the structure of T as an inference site for K, potentially widening K when T carries multiple tags. With NoInfer<TagName> in the constraint, K is inferred only from the explicit tagName argument — which is the intended semantics. The tagged value's structure should validate the lookup, not determine the tag name.

What was reviewed

All source types in source/ were reviewed for NoInfer applicability. Most type-fest types are pure type-level utilities that don't involve competing inference sites for the same type parameter — NoInfer is primarily beneficial in function generics, and most type-fest types are used as explicit type arguments rather than inferred from multiple argument positions simultaneously.

GetTagMetadata is the clearest case: it has both a constraint-based inference site and an explicit parameter for the same TagName variable, making NoInfer semantically correct.

Tests

All existing tests pass:

• test-d/opaque.ts — covers Tagged, GetTagMetadata, UnwrapTagged, etc.
• TypeScript compiler (tsc --noEmit) passes with no errors.

Closes #848