feat: use Backend.AI cluster SSH key for auto-detected environments (#16)

Author: inureyes

src/config.rs

@@ -225,7 +225,10 @@ impl Config {
 
         Some(Cluster {
             nodes: filtered_nodes,
-            defaults: ClusterDefaults::default(),
+            defaults: ClusterDefaults {
+                ssh_key: Some("/home/config/ssh/id_cluster".to_string()),
+                ..ClusterDefaults::default()
+            },
             interactive: None,
         })
     }

tests/backendai_env_test.rs

@@ -51,6 +51,13 @@ async fn test_backendai_env_auto_detection() {
     // Get the bai_auto cluster
     let cluster = config.clusters.get("bai_auto").unwrap();
 
+    // Verify SSH key is set to Backend.AI cluster key
+    assert_eq!(
+        cluster.defaults.ssh_key,
+        Some("/home/config/ssh/id_cluster".to_string()),
+        "Backend.AI cluster should use /home/config/ssh/id_cluster as SSH key"
+    );
+
     // Verify nodes were parsed correctly
     assert_eq!(cluster.nodes.len(), 3);
 
@@ -66,6 +73,13 @@ async fn test_backendai_env_auto_detection() {
     assert_eq!(nodes[1].host, "node2.ai");
     assert_eq!(nodes[2].host, "node3.ai");
 
+    // Verify get_ssh_key returns the correct key for Backend.AI cluster
+    assert_eq!(
+        config.get_ssh_key(Some("bai_auto")),
+        Some("/home/config/ssh/id_cluster".to_string()),
+        "get_ssh_key should return Backend.AI cluster key path"
+    );
+
     // Restore original env vars
     unsafe {
         if let Some(val) = orig_hosts {