hive-forge: dedup the --json refusal into refuse_json(), test it, cover attachment-get/artifact-get too

hive-forge/src/verbs/artifact_get.rs

@@ -26,6 +26,7 @@ use clap::Args as ClapArgs;
 use forgejo_api::structs::ListActionRunsQuery;
 
 use crate::client::Client;
+use crate::verbs::refuse_json;
 
 #[derive(ClapArgs)]
 pub struct Args {
@@ -82,6 +83,11 @@ fn resolve_run_id(client: &Client, repo: &str, run_number: u64) -> Result<i64> {
 /// download fails (network, or a non-2xx status such as `404` for an
 /// unknown artifact name), or if the output path can't be written.
 pub fn run(client: &Client, args: Args) -> Result<()> {
+    refuse_json(
+        client.json_mode(),
+        "artifact-get",
+        "it downloads the raw artifact zip, there is no JSON form",
+    )?;
     let repo = client.repo()?;
     let run_id = resolve_run_id(client, repo, args.run)?;
     let url = client.web_url(&format!(