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

bin/quak.ts

@@ -123,7 +123,6 @@ program
     .description("Download and decrypt a single file")
     .argument("<fileID>", "File ID (from `quak files`)")
     .option("--out <path>", "Output file path")
-    .option("--collection <id>", "Accepted for compatibility; ignored")
     .action((fileID: string, opts: { out?: string }) =>
         run(getCommand(context(), fileID, opts)),
     );
@@ -133,7 +132,6 @@ program
     .description("Download and decrypt a thumbnail")
     .argument("<fileID>", "File ID (from `quak files`)")
     .option("--out <path>", "Output file path")
-    .option("--collection <id>", "Accepted for compatibility; ignored")
     .action((fileID: string, opts: { out?: string }) =>
         run(getThumbCommand(context(), fileID, opts)),
     );