fix(javascript): keep exports out of write relations

Project writes only from write-role references. Export references remain distinct facts and genuine assignments still traverse writes-only traces.

Validation: source semantic controls and public CLI/MCP writes-only traces.

Fixes #3207

src/application/javascript/JavaScriptSemanticGraphBuilder.ts

@@ -648,7 +648,7 @@ function* projectDefinitionsAndReferences(
         resolution: "resolved",
         evidence: inferredSemanticEvidenceAt(context.file, reference.location),
       });
-    else
+    else if (reference.role === "write")
       addRelation(context.state, {
         source: expression,
         target: binding,