fix(javascript): parse declaration artifacts in ambient mode

src/domain/javascript/javascriptSourceParser.ts

@@ -1,4 +1,4 @@
-import { parse } from "@babel/parser";
+import { parse, type ParserPlugin } from "@babel/parser";
 
 /** Babel AST produced by REA's inert JavaScript parser boundary. */
 export type ParsedJavaScriptSource = ReturnType<typeof parse>;
@@ -8,6 +8,10 @@ export const parseJavaScriptSource = (
   source: string,
   sourcePath?: string,
 ): ParsedJavaScriptSource | null => {
+  const typescript: ParserPlugin = [
+    "typescript",
+    { dts: /\.d\.(?:ts|mts|cts)$/iu.test(sourcePath ?? "") },
+  ];
   try {
     return parse(source, {
       sourceType: "unambiguous",
@@ -17,12 +21,11 @@ export const parseJavaScriptSource = (
       // forms, including parameter decorators. Without it a decorated
       // TypeScript source fails to parse at all rather than reporting
       // recovered syntax, which loses every fact derived from that source.
-      // Plain .ts artifacts admit angle-bracket type assertions instead of JSX.
+      // Plain .ts and .cts artifacts admit angle-bracket type assertions instead of JSX.
       // Unknown paths retain the existing JSX-capable parser contract.
-      plugins:
-        sourcePath?.toLowerCase().endsWith(".ts") === true
-          ? ["decorators-legacy", "typescript"]
-          : ["decorators-legacy", "jsx", "typescript"],
+      plugins: /\.(?:ts|cts)$/iu.test(sourcePath ?? "")
+        ? ["decorators-legacy", typescript]
+        : ["decorators-legacy", "jsx", typescript],
     });
   } catch (cause: unknown) {
     // Unparseable source is represented by the null return.