quak files COLLECTION fetches that collection's files alone (closes #217)

`quak files` with a collection ID used to wait for a full refresh, which
on an empty cache fetched the files of every collection in the account.
It now reads the collection list, then that one collection's files
through the new `Library.freshFiles()`, and stores nothing. The files
print in the server's order, and no refresh progress lines appear. Each
file prints once, as the latest copy the server sent. `quak files`
without a collection ID still waits for a refresh.

Some tests ran `quak files` with a collection ID to fill the cache, to
show a refresh's progress or to show what `-q` hides. They now run a
command that still refreshes.

Model: opus-5-5

test/cli/log.test.ts

@@ -237,10 +237,10 @@ describe("-q", () => {
     // The refresh's progress is left out; the line saying why the command
     // failed is the fatal one, and it is printed.
     it("prints only the line a failing command exits with", async () => {
-        expect(await quak("-q", "files", "9")).toEqual({
+        expect(await quak("-q", "get", "999")).toEqual({
             code: 1,
             stdout: "",
-            stderr: "Collection 9 not found\n",
+            stderr: "File 999 not found\n",
         });
     });