implement Enum::Variant match patterns in parser and both codegens

Parser now handles `SomeEnum::Variant` in match arm patterns, emitting
a Variant pattern node with enum_name and variant fields. Previously
these fell through to Binding, producing broken codegen.

JS codegen: emit str_eq check against the variant name string (El enums
are plain strings at runtime). C codegen: same, via EL_STR + str_eq.

Rebuild elc to pick up the parser change.

el-compiler/src/parser.el

@@ -408,6 +408,13 @@ fn parse_pattern(tokens: [Map<String, Any>], pos: Int) -> Map<String, Any> {
         if v == "_" {
             return make_result({ "pattern": "Wildcard" }, pos + 1)
         }
+        // Check for Enum::Variant pattern (Color::Red, Status::Ok, etc.)
+        // Lexed as: Ident ColonColon Ident
+        let next_k = tok_kind(tokens, pos + 1)
+        if next_k == "ColonColon" {
+            let variant_name = tok_value(tokens, pos + 2)
+            return make_result({ "pattern": "Variant", "enum_name": v, "variant": variant_name }, pos + 3)
+        }
         return make_result({ "pattern": "Binding", "name": v }, pos + 1)
     }
     if k == "Int" {