fix(desktop): stop labeling malformed relay responses as unreachable

parse_json_response tagged a 2xx response with an undeserializable body
as "relay unreachable:", the same prefix used for genuine transport
failures. The reconcile log-guard suppresses that prefix, so a reached-but-
malformed response (protocol mismatch, relay bug, corrupted body) was being
silently swallowed instead of surfaced. Re-prefix it to "relay returned
malformed response:" so it falls outside the unreachable bucket and logs
loudly; the frontend connectivity classifier also correctly stops treating
it as a connectivity failure. No other code reads the old string.

Co-authored-by: Will Pfleger <pfleger.will@gmail.com>
Signed-off-by: Will Pfleger <pfleger.will@gmail.com>

desktop/src-tauri/src/relay.rs

@@ -211,11 +211,16 @@ pub(crate) async fn parse_json_response<T: DeserializeOwned>(
         return Err(msg);
     }
 
-    // Drop the reqwest error detail — it contains the raw URL.
+    // A successful HTTP response whose body fails to deserialize means the relay
+    // was reached but returned something unexpected (protocol mismatch, relay bug,
+    // corrupted body) — NOT a connectivity failure. Keep it off the
+    // "relay unreachable:" bucket so it surfaces loudly instead of being treated
+    // as a transient unreachable-relay condition. The reqwest error detail is
+    // dropped because it contains the raw URL.
     response
         .json::<T>()
         .await
-        .map_err(|_| "relay unreachable: response was not valid JSON".to_string())
+        .map_err(|_| "relay returned malformed response: not valid JSON".to_string())
 }
 
 pub async fn relay_error_message(response: reqwest::Response) -> String {