feat(readarr): fetch Readarr authors and expose them on the CLI

Add ReadarrEvent::ListAuthors, mapping to GET /author, and wire it up as
`managarr readarr list authors`.

This is the first Readarr event that touches the library rather than
configuration, so it creates the library/authors module tree mirroring
Lidarr's library/artists layout.

list_authors mirrors Lidarr's list_artists, including the sort-prompt
route guard: a response landing while the user has the sort prompt open
must not clobber their in-progress sort selection. Both directions of
that guard are covered by tests.

src/cli/readarr/list_command_handler.rs

@@ -17,6 +17,8 @@ mod list_command_handler_tests;
 
 #[derive(Debug, Clone, PartialEq, Eq, Subcommand)]
 pub enum ReadarrListCommand {
+  #[command(about = "List all authors in your Readarr library")]
+  Authors,
   #[command(about = "List disk space details for all provisioned root folders in Readarr")]
   DiskSpace,
   #[command(about = "Fetch Readarr logs")]
@@ -72,6 +74,13 @@ impl<'a, 'b> CliCommandHandler<'a, 'b, ReadarrListCommand> for ReadarrListComman
 
   async fn handle(self) -> Result<String> {
     let result = match self.command {
+      ReadarrListCommand::Authors => {
+        let resp = self
+          .network
+          .handle_network_event(ReadarrEvent::ListAuthors.into())
+          .await?;
+        serde_json::to_string_pretty(&resp)?
+      }
       ReadarrListCommand::DiskSpace => {
         let resp = self
           .network

src/cli/readarr/list_command_handler_tests.rs

@@ -26,6 +26,7 @@ mod tests {
     #[rstest]
     fn test_list_commands_have_no_arg_requirements(
       #[values(
+        "authors",
         "disk-space",
         "metadata-profiles",
         "quality-profiles",
@@ -87,6 +88,29 @@ mod tests {
       network::{MockNetworkTrait, NetworkEvent, readarr_network::ReadarrEvent},
     };
 
+    #[tokio::test]
+    async fn test_handle_list_authors_command() {
+      let mut mock_network = MockNetworkTrait::new();
+      mock_network
+        .expect_handle_network_event()
+        .with(eq::<NetworkEvent>(ReadarrEvent::ListAuthors.into()))
+        .times(1)
+        .returning(|_| {
+          Ok(Serdeable::Readarr(ReadarrSerdeable::Value(
+            json!({"testResponse": "response"}),
+          )))
+        });
+      let app_arc = Arc::new(Mutex::new(App::test_default()));
+      let list_authors_command = ReadarrListCommand::Authors;
+
+      let result =
+        ReadarrListCommandHandler::with(&app_arc, list_authors_command, &mut mock_network)
+          .handle()
+          .await;
+
+      assert_ok!(&result);
+    }
+
     #[tokio::test]
     async fn test_handle_list_disk_space_command() {
       let mut mock_network = MockNetworkTrait::new();