Make backup wait for the server refresh and fail when it fails (closes #99)

lib.backup() refreshed through the background loop's refresh, which returns
at once when one is already running and swallows a failure, so a backup
could run on the previous file list, or on an empty cache, and exit 0. It
now uses the refresh fresh() uses: it joins a running refresh or starts
one, and rejects before touching any file when it fails. The CLI's error
wrapper prints that as one line and exits 1.

Model: opus-5-5

test/cli/commands.test.ts

@@ -20,6 +20,7 @@ import {
 } from "node:fs";
 import { join } from "node:path";
 import { tmpdir } from "node:os";
+import { PassThrough } from "node:stream";
 import { describe, it, expect, beforeAll, beforeEach, afterEach } from "vitest";
 
 import {
@@ -34,6 +35,7 @@ import {
     backupCommand,
     listMissingThumbnailsCommand,
 } from "../../src/cli-commands.js";
+import { run } from "../../src/cli-run.js";
 import { loadSession } from "../../src/cli-session.js";
 import type { Client, ClientSnapshot } from "../../src/client.js";
 import type { ContentSource } from "../../src/library/content.js";
@@ -430,6 +432,34 @@ describe("backup", () => {
         expect(result.errors[0].fileID).toBe(101);
         expect(stderr.text).toBe("Starting backup...\n");
     });
+
+    it("exits 1 with the error on one line when the refresh fails", async () => {
+        const client = {
+            ...fakeClient(),
+            collectionsSince: async () => {
+                throw new Error("HTTP 401 from server");
+            },
+        } as unknown as Client;
+        const dir = join(root, "backup");
+        // Through `run`, as `bin/quak.ts` does, which prints a thrown error.
+        const runStderr = new PassThrough();
+        let runText = "";
+        runStderr.on("data", (chunk: Buffer) => {
+            runText += chunk.toString();
+        });
+        const code = await new Promise<number>((resolve) => {
+            void run(
+                backupCommand(context(client), dir, {}),
+                new PassThrough(),
+                runStderr,
+                resolve,
+            );
+        });
+        expect(code).toBe(1);
+        expect(runText).toBe("quak: HTTP 401 from server\n");
+        expect(stderr.text).toBe("Starting backup...\nRefreshing library...\n");
+        expect(existsSync(join(dir, "originals"))).toBe(false);
+    });
 });
 
 describe("helper list-missing-thumbnails", () => {