Document style handling for 2D booleans and other methods

Applying a boolean operation to a `MeshSized` entity returns a bare `ClippedPolygon` (or `CurvilinearRegion` for the `_curved` variants) with no sizing information and no warning. Transforms (`translate`, `rotate`, `Reflection`, …) preserve the style, so users might reasonably expect booleans to as well — the style is an annotation, not geometry.

Similarly, `OptionalStyle` is resolved to its default, `Rounded` is discretized by non-curved variants, `ToTolerance` discretizes curves even in `_curved` variants.

`offset` and `halo` are similar.

This should all be documented. We could also consider preserving the style when unambiguous.

Locate the documentation entry points for 2D booleans, their _curved variants, offset, halo, and transforms. Document the observed handling of MeshSized, OptionalStyle, Rounded, and ToTolerance styles, including when curves are discretized or sizing information is lost. Done means users can find and understand these behaviors and the possible style-preservation consideration.

Written by the indexing model from the issue text.