status shows each home relay: connected, down with the error, or denied

iroh 1.3's home_relay_status, on GlobalStatus as relays (absent when
empty, so older clients parse it). The thing we lacked when fetches
timed out: whether this daemon can be reached through a relay at all.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

varde-proto/src/lib.rs

@@ -324,6 +324,27 @@ pub struct GlobalStatus {
     pub pins: u64,
     /// Number of connected trusted peers.
     pub connected_peers: u64,
+    /// The home relays this endpoint uses and how each is doing. Empty
+    /// when relays are off (LAN-only) or on a daemon before 0.1.10.
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub relays: Vec<RelayInfo>,
+}
+
+/// One home relay's connection state (iroh's `home_relay_status`).
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct RelayInfo {
+    /// The relay URL.
+    pub url: String,
+    /// Whether the endpoint holds a connection to it right now.
+    pub connected: bool,
+    /// The most recent connection error, when not connected and an
+    /// attempt has failed; for a person to read, not to match on.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub last_error: Option<String>,
+    /// The relay's reason when it denied this endpoint's authentication:
+    /// the one failure retrying will not cure.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub auth_denied: Option<String>,
 }
 
 /// Status of one hash.
@@ -478,4 +499,13 @@ mod tests {
             _ => panic!("wrong variant"),
         }
     }
+
+    #[test]
+    fn a_status_from_before_relays_still_parses() {
+        let old = r#"{"version":"0.1.9","protocol":2,"store_path":"/s","pins":1,"connected_peers":0}"#;
+        let status: GlobalStatus = serde_json::from_str(old).unwrap();
+        assert!(status.relays.is_empty());
+        let back = serde_json::to_string(&status).unwrap();
+        assert!(!back.contains("relays"), "empty stays absent for old clients: {back}");
+    }
 }