quak get and get-thumb on an empty cache stop fetching collections once they find the file (closes #222)

`quak get` and `quak get-thumb` used to wait for a refresh, which on an
empty cache fetched the files of every collection. Now, on an empty
cache, `freshFile` reads the collection list, then one collection's
files at a time, and stops at the first that holds the file. That search
stores nothing. Once the cache holds the account's collections,
`freshFile` refreshes as before and looks the file up in the cache. The
commands fetch the content through the new `Library.originalOf()` and
`Library.thumbnailOf()`, which take the file record itself, since the
store may not hold it.

On an empty cache they no longer print a refresh's progress lines. The
`-q` test that relied on `get` refreshing now runs
`helper fix-missing-thumbnails`.

Model: opus-5-5

test/library/content.test.ts

@@ -375,6 +375,25 @@ describe("ContentCache.original / thumbnail", () => {
         await cache.open();
         await expect(cache.original(999)).rejects.toThrow(/unknown file/i);
     });
+
+    // `getFile` knows no file here, so the cache can fetch only the file it is
+    // given.
+    it("originalOf and thumbnailOf fetch and cache the file they are given", async () => {
+        const { cache, source } = buildCache({ files: [] });
+        await cache.open();
+
+        const original = await cache.originalOf(file(5));
+        const thumbnail = await cache.thumbnailOf(file(5));
+
+        expect(source.originalCalls).toEqual([5]);
+        expect(source.thumbnailCalls).toEqual([5]);
+        expect(original.path).toBe(join(cacheDir, "originals", "5.jpg"));
+        expect(thumbnail.path).toBe(join(cacheDir, "thumbnails", "5.jpg"));
+        expect(cache.pathsFor(5)).toEqual({
+            originalPath: original.path,
+            thumbnailPath: thumbnail.path,
+        });
+    });
 });
 
 describe("ContentCache.ensureThumbnails", () => {