M6: transliterate non-ASCII layer names into code-export class names (#1235)

class_name runs layer names through deunicode (new dependency: pure Rust
tables, zero deps, BSD-3-Clause, the slug crate's base) before its ASCII
filter, so Korean, Cyrillic, Latin-diacritic and CJK names become
readable ASCII classes in HTML/CSS/React/Leptos output, component roots
and data-* variant attributes: 로그인 화면 → rogeuin-hwamyeon, кнопка →
knopka, über → uber, 按钮 → an-niu (before, every one came out layer-,
layer--2, ...). Symbols-only names take the node's kind (.text, .frame)
instead of layer-, the 40-character cut lands on a word boundary, and a
leading digit keeps the layer- prefix. SwiftUI/Compose type names are
unchanged (their own sanitizer); ASCII-only names are byte-identical.
html_codegen_tests updated and extended.

crates/engine/src/component_codegen.rs

@@ -618,7 +618,7 @@ pub fn definition(doc: &Document, c: &Component, lang: CodeLang) -> String {
 /// `data-*` attribute names for variant parameters, unique among them (in order).
 fn data_attrs(variants: &[&Param]) -> Vec<String> {
     let mut used = Vec::new();
-    variants.iter().map(|p| format!("data-{}", class_name(&p.prop, &mut used))).collect()
+    variants.iter().map(|p| format!("data-{}", class_name(&p.prop, "prop", &mut used))).collect()
 }
 
 /// `c`'s markup in React or Leptos (two levels in) and its stylesheet (variables as custom
@@ -626,7 +626,7 @@ fn data_attrs(variants: &[&Param]) -> Vec<String> {
 fn web(doc: &Document, c: &Component, lang: CodeLang) -> (String, String, String) {
     let ctx = Ctx { doc, root: c.comp, comp: Some(c), base: 2 };
     let root_name = c.set.and_then(|s| doc.node(s)).or_else(|| doc.node(c.comp)).map(|n| n.name.clone()).unwrap_or_default();
-    let root_class = class_name(&root_name, &mut Vec::new());
+    let root_class = class_name(&root_name, "component", &mut Vec::new());
     let variants: Vec<&Param> = c.params.iter().filter(|p| matches!(p.kind, ParamKind::Variant(_))).collect();
     let attr_names = data_attrs(&variants);
     let pass = |root: NodeId| {