fix(review): log transport errors before treating as failed probe

The previous fix used `unwrap_or(false)` which silently discarded the
error details. Operators debugging why a worker won't come Ready had no
visibility into the underlying cause (connection refused, TLS failure,
DNS resolution failure, timeout, etc.).

Switched to `unwrap_or_else` which logs the error with the worker URL
at warn level before returning false. This preserves the existing
state-machine behavior (transport errors still count as failed probes
and feed the Pending timeout / NotReady→Failed paths) while making the
underlying cause discoverable from logs.

Refs: PR #1102 review feedback
Signed-off-by: Simo Lin <linsimo.mark@gmail.com>

Author: slin1237

model_gateway/src/worker/worker.rs

@@ -610,14 +610,23 @@ impl Worker for BasicWorker {
             self.total_pending_probes.fetch_add(1, Ordering::Relaxed);
         }
 
-        // Transport-level errors (e.g. gRPC connect failure) are treated as
-        // failed probes rather than short-circuiting, so the Pending timeout
-        // and NotReady→Failed paths can observe them.
-        let probe_result = match &self.metadata.spec.connection_mode {
+        // Transport-level errors (e.g. gRPC connect failure, TLS handshake
+        // failure, DNS resolution failure) are treated as failed probes
+        // rather than short-circuiting, so the Pending timeout and
+        // NotReady→Failed paths can observe them. The error is logged with
+        // the worker URL so operators can debug why a worker won't come Ready.
+        let health_result = match &self.metadata.spec.connection_mode {
             ConnectionMode::Http => self.http_health_check().await,
             ConnectionMode::Grpc => self.grpc_health_check().await,
-        };
-        let health_result = probe_result.unwrap_or(false);
+        }
+        .unwrap_or_else(|err| {
+            tracing::warn!(
+                worker_url = %self.metadata.spec.url,
+                error = %err,
+                "Health check probe transport error (treating as failed probe)"
+            );
+            false
+        });
 
         if health_result {
             self.consecutive_failures.store(0, Ordering::Release);