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.test.ts

@@ -25,6 +25,43 @@ import { semanticCoverageResourceLimits } from "../../domain/javascript/javascri
 
 const SHA256 = "a".repeat(64);
 
+it.each([
+  ["plain export", "const answer = 42; export { answer };", 0],
+  ["aliased export", "const answer = 42; export { answer as result };", 0],
+  ["declaration only", "const answer = 42;", 0],
+  ["genuine assignment", "let answer = 0; answer = 1;", 1],
+])(
+  "projects writes only for actual writes: %s",
+  (_name, source, writeCount) => {
+    const graph = graphFor(source);
+    const binding = graph.nodes.find(
+      ({ kind, label }) => kind === "binding" && label === "answer",
+    );
+    if (binding === undefined) throw new Error("Expected answer binding");
+    const writes = graph.relations.filter(
+      ({ relation, target_node_id }) =>
+        relation === "writes" && target_node_id === binding.node_id,
+    );
+    expect(writes).toHaveLength(writeCount);
+    const exportReference = graph.nodes.find(
+      ({ identity }) => identity.role_key === "reference:0:export:answer",
+    );
+    if (source.includes("export {")) expect(exportReference).toBeDefined();
+
+    const trace = queryJavaScriptSemanticGraph(graph, {
+      seed: { kind: "semantic-node", node_id: binding.node_id },
+      direction: "backward-provenance",
+      allowed_relations: ["writes"],
+    });
+    expect(trace.status).toBe("found");
+    expect(trace.summary).toMatchObject({
+      total_seed_matches: 1,
+      traversed_relations: writeCount,
+    });
+    expect(trace.relations).toHaveLength(writeCount);
+  },
+);
+
 it("projects closure and direct interprocedural flow without execution", () => {
   const graph = graphFor(`
       const outer = 2;