Boolean props follow the HTML presence/absence semantics.
- We stick close to standard HTML behavior: flag="false" is treated as
true in most cases. Standard bare attributes disabled and required for
form fields are interpreted as true with non-existence as false.
- The use-cases for aria-*="false" and contenteditable="false" are also
supported by typing them in the JS class as string ("true" | "false").
This "true" | "false" opt-in is types-only. At runtime it's just a
string, and strings already serialize literally and are never removed —
so the enumerated/aria path needs no runtime code.
