#[derive(jedem::Enum)]: each language gets a real enum

[zmaril]

Stacked on #8. The last of the five, and the one whose cost was never really
about lines.

jawohl had to write a describe() converter turning Validation into a
String, so Python received 'irrecoverably_invalid' as a bare string and
TypeScript received string. The API was degraded to fit the vocabulary.

hello.classify(20)              # Ripeness.Done      — a real class
hello.is_settled("Done")        # TypeError          — a bare string is rejected

hello.classify(20)              // "Done"            — a TS string-literal union
hello.isSettled("NotAVariant")  // throws

Python gets a pyclass registered on the module; TypeScript gets napi's
string_enum. Both reject non-variants — a typo is caught by that language's
own tooling instead of surfacing as a value nobody matched. Variants take an
optional boundary spelling via #[jedem(name = "...")].

Three things the implementation forced

Wire names must be valid identifiers. My first draft allowed "n/a", which
made the pyclass macro fail to expand and cascaded into seven confusing errors
in Python only — the worst place to find out. A variant has to be nameable
in every target, so the derive rejects non-identifiers with a message saying why.

From<A> for B does not give Option<A> → Option<B>. Conversion is mapped
through containers by a shared convert() helper, so Option<Ripeness> and
Vec<Ripeness> work rather than failing at the binding's compile step.

Enums are collected by walking the ops, not listed in surface!, because the
macro cannot resolve types. That also means an enum reached only through an
Option is still declared — otherwise a binding names a type it never defined.

And a nicer error for everything else

An unknown named type now lowers as an enum, with the curated "jedem cannot lower
this" message moved to a diagnostic::on_unimplemented on the EnumType trait —
so a genuinely unsupported type still gets the explanation, including that there
is deliberately no opaque-blob fallback.

Adding the Type variant made both backends fail to compile until they
handled it. That is the exhaustiveness safety net working as designed.

43 tests, clippy clean, both round-trips exercising enums as returns, as
parameters, and inside Option.

🤖 Generated with Claude Code

https://claude.ai/code/session_01HsDxLrGdx6nPaXkVEWkNvS