grammars: Highlight class instantiations in JavaScript, TypeScript, and TSX (#61890)

## Why

JavaScript, TypeScript, and TSX class declarations were captured as
`type.class`, but the same class names in `new` expressions were
captured as the generic `type`. Themes that define a distinct style for
`type.class` therefore rendered declarations and instantiations
inconsistently.

## What

Update the three highlight queries so constructor identifiers in `new`
expressions use `type.class`. Themes without a dedicated `type.class`
style continue to fall back to their existing `type` style.

Add a regression test that loads the real JavaScript, TypeScript, and
TSX grammars with distinct colors for `type` and `type.class`, then
verifies that both the declaration and instantiation receive the
class-specific highlight.

## Testing

- `cargo test -p languages test_class_instantiation_highlighting`
- `cargo test -p languages`
- `cargo fmt --all -- --check`
- `./script/clippy -p languages`

## References

Closes #55943

Release Notes:

- Fixed inconsistent class instantiation highlighting in JavaScript,
TypeScript, and TSX.

crates/grammars/src/javascript/highlights.scm

@@ -30,7 +30,7 @@
     ] @function.method))
 
 (new_expression
-  constructor: (identifier) @type)
+  constructor: (identifier) @type.class)
 
 (nested_type_identifier
   module: (identifier) @type)

crates/grammars/src/tsx/highlights.scm

@@ -30,7 +30,7 @@
     ] @function.method))
 
 (new_expression
-  constructor: (identifier) @type)
+  constructor: (identifier) @type.class)
 
 (nested_type_identifier
   module: (identifier) @type)

crates/grammars/src/typescript/highlights.scm

@@ -123,7 +123,7 @@
     ] @function.method))
 
 (new_expression
-  constructor: (identifier) @type)
+  constructor: (identifier) @type.class)
 
 (nested_type_identifier
   module: (identifier) @type)

crates/languages/src/typescript.rs

@@ -908,10 +908,12 @@ async fn get_cached_ts_server_binary(
 mod tests {
     use std::path::Path;
 
-    use gpui::{AppContext as _, BackgroundExecutor, TestAppContext};
+    use gpui::{AppContext as _, BackgroundExecutor, Hsla, TestAppContext};
     use project::FakeFs;
+    use rope::Rope;
     use serde_json::json;
     use task::TaskTemplates;
+    use theme::SyntaxTheme;
     use unindent::Unindent;
     use util::{path, rel_path::rel_path};
 
@@ -919,6 +921,34 @@ mod tests {
         PackageJsonData, TypeScriptContextProvider, replace_test_name_parameters,
     };
 
+    #[test]
+    fn test_class_instantiation_highlighting() {
+        let source = Rope::from("class Dog {}\nconst dog = new Dog();");
+        let theme = SyntaxTheme::new_test([("type", Hsla::blue()), ("type.class", Hsla::green())]);
+
+        for language in [
+            crate::language(
+                "typescript",
+                tree_sitter_typescript::LANGUAGE_TYPESCRIPT.into(),
+            ),
+            crate::language("tsx", tree_sitter_typescript::LANGUAGE_TSX.into()),
+            crate::language("javascript", tree_sitter_typescript::LANGUAGE_TSX.into()),
+        ] {
+            language.set_theme(&theme);
+            let class_highlight = language
+                .grammar()
+                .and_then(|grammar| grammar.highlight_id_for_name("type.class"))
+                .expect("type.class highlight should be defined");
+
+            assert_eq!(
+                language.highlight_text(&source, 0..source.len()),
+                vec![(6..9, class_highlight), (29..32, class_highlight)],
+                "{} class instantiations should use the type.class highlight",
+                language.name()
+            );
+        }
+    }
+
     #[gpui::test]
     async fn test_outline(cx: &mut TestAppContext) {
         for language in [