perf(javascript): reduce retained semantic analysis allocations (#1601)

Reduce retained semantic allocations and memoize lexical scope ancestry while preserving semantic identities. Refs #1065 and #1563; the complete-directory memory failure remains open.

src/domain/javascript/javascriptSemanticReturns.ts

@@ -83,7 +83,14 @@ const semanticReturnSiteId = (
   callableId: string,
   location: JavaScriptSemanticReturnSite["location"],
 ): string =>
-  `${callableId}:return:${String(location.start.line)}:${String(location.start.column)}:${String(location.end.line)}:${String(location.end.column)}`;
+  [
+    callableId,
+    "return",
+    String(location.start.line),
+    String(location.start.column),
+    String(location.end.line),
+    String(location.end.column),
+  ].join(":");
 
 /** Link exports to callables only when lexical resolution is unique and exact. */
 export const resolveSemanticModuleCallables = (