Implement the `String.fromCodePoint(_)` primitive that creates a string from a Unicode code point, with validation for integer range 0–0x10ffff. Extract inline UTF-8 encoding logic from `readUnicodeEscape` in the compiler into new `wrenUtf8NumBytes` and `wrenUtf8Encode` utility functions in `wren_utils`, and add `wrenStringFromCodePoint` helper in `wren_value`. Update documentation for core classes to add "Methods" and "Static Methods" section headers, and include `String.fromCodePoint` docs with example. Add a test file `from_code_point.wren` covering various code points.
Implement a new `supertype` property on Class objects that returns the superclass of a given class. The primitive `class_supertype` checks if the class has a superclass (returning null for Object) and returns the superclass object. Includes documentation in the class reference and a test file verifying behavior for explicit superclasses, implicit Object inheritance, and Object's null supertype.
Bob Nystrom