Remove the no-op --collection option from get and get-thumb (closes #241)

Both commands listed `--collection <id>` as accepted and ignored. It now
is refused as an unknown option, and the README no longer mentions it.

Model: opus-5-5

test/cli/bin.test.ts

@@ -1,8 +1,9 @@
 /**
  * Tests for the retry options `bin/quak.ts` loads the saved session with
  * (`quak backup` gets the unattended ones, every other command the default),
- * each with the callbacks that log its requests and retries, and for
- * `quak files` taking its collection ID as an optional argument.
+ * each with the callbacks that log its requests and retries, for `quak files`
+ * taking its collection ID as an optional argument, and for `quak get` and
+ * `quak get-thumb` refusing `--collection`.
  *
  * Each test runs `bin/quak.ts`, as the smoke test does, with its session loader
  * replaced by one that records the options it is given and reports no session,
@@ -105,3 +106,14 @@ describe("bin/quak.ts files", () => {
         expect(await quak("files", "7")).toMatch(/^Not logged in/);
     });
 });
+
+describe("bin/quak.ts get and get-thumb", () => {
+    it.each(["get", "get-thumb"])(
+        "%s refuses --collection as an unknown option",
+        async (command) => {
+            expect(await quak(command, "1", "--collection", "2")).toMatch(
+                /^error: unknown option '--collection'/,
+            );
+        },
+    );
+});