Add map import and export with durable refresh progress

tests/map-refresh.test.ts

@@ -0,0 +1,27 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { refreshCapture } from "../shared/map-refresh";
+
+const original = {
+  id: "original",
+  name: "My Minecraft map",
+  created_at: "2026-10-07T09:51:39Z",
+};
+const contribution = {
+  id: "accepted",
+  name: "My Minecraft map",
+  created_at: "2026-10-07T10:28:01Z",
+};
+test("refresh chooses the newest eligible capture, including newly accepted contributions with the same name", () => {
+  assert.equal(refreshCapture([original]), "original");
+  assert.equal(refreshCapture([original, contribution]), "accepted");
+  assert.equal(refreshCapture([contribution, original]), "accepted");
+});
+test("a deliberately selected older capture stays selected when the list reloads", () => {
+  assert.equal(
+    refreshCapture([contribution, original], "original"),
+    "original",
+  );
+  assert.equal(refreshCapture([contribution], "original"), "accepted");
+  assert.equal(refreshCapture([]), "");
+});