fix: preserve evidence revision staleness semantics

backend/test/routes-workspaces.test.ts

@@ -321,6 +321,25 @@ test("returns a 409 field conflict instead of overwriting a changed workspace",
   });
 });
 
+test("maps a stale registry commit to HTTP 409 without conflict payloads", async () => {
+  const registry = registryFake({
+    publish: vi.fn(async () => {
+      throw new WorkspaceRegistryError("workspace_stale", "Workspace revision is stale");
+    }),
+  });
+  const app = appFor(registry);
+
+  const res = await app.inject({ method: "POST", url: "/workspaces/publish", payload: {
+    action: "update",
+    workspace,
+    baseCommit: "c".repeat(40),
+    baseBlob: "d".repeat(40),
+  } });
+
+  expect(res.statusCode).toBe(409);
+  expect(res.json()).toEqual({ code: "workspace_stale", message: "Workspace revision is stale." });
+});
+
 test("exports generated public artifacts without secret values", async () => {
   const app = appFor(registryFake());