Custom elements are the public API, the facade only constructs them

Editors write Lit templates and examples want Tweakpane ergonomics, so the package ships both: custom elements are the implementation and the public surface, and a builder facade (Pane, addFolder, addBinding) constructs those same elements with no rendering of its own.

Considered Options

• An imperative builder only, a Tweakpane clone. Editors would rewrite working Lit templates as builder calls.
• Elements only, no facade. Examples would keep Tweakpane, and the deduplication goal fails.