Add comprehensive logging for debugging polling issues

Added detailed logging to diagnose two issues:

1. **Unknown status detection**: When the deployment status shows as
   "unknown", we now log the actual stage value received from HuggingFace
   and list all known stages. This helps identify if HuggingFace has
   introduced new stages we don't recognize yet.

2. **Health check failures**: Override _check_deployment_health with
   better logging to show:
   - The exact health check URL being tested
   - Whether health check passed or failed
   - Specific error messages when health check fails
   - Status codes returned from the endpoint

These logs will help diagnose why deployments continue polling even
when the Space appears to be running and the health endpoint is working.

The logs now show stage transitions and health check results at INFO
level for easier debugging without requiring DEBUG logging.

Author: claude

src/zenml/integrations/huggingface/deployers/huggingface_deployer.py

@@ -548,6 +548,11 @@ def do_get_deployment_state(
                 status = DeploymentStatus.ABSENT
             else:
                 # Unknown/future stages
+                logger.warning(
+                    f"Space {space_id} has unrecognized stage: '{runtime.stage}'. "
+                    f"This might be a new HuggingFace stage. Treating as UNKNOWN. "
+                    f"Known stages: {[s.value for s in SpaceStage]}"
+                )
                 status = DeploymentStatus.UNKNOWN
 
             # Get deployment URL from Space domains (only when fully ready)
@@ -560,7 +565,8 @@ def do_get_deployment_state(
             ):
                 url = f"https://{domains[0]['domain']}"
                 logger.info(
-                    f"Space {space_id} deployment URL: {url} (status={status})"
+                    f"Space {space_id} deployment URL: {url} "
+                    f"(status={status}, stage={runtime.stage}, domain_stage={domain_stage})"
                 )
 
             return DeploymentOperationalState(
@@ -578,6 +584,75 @@ def do_get_deployment_state(
                 f"Space {space_id} not found: {e}"
             ) from e
 
+    def _check_deployment_health(
+        self,
+        deployment: DeploymentResponse,
+    ) -> bool:
+        """Check if the deployment is healthy by calling its health check endpoint.
+
+        Overrides base method to add better logging for debugging.
+
+        Args:
+            deployment: The deployment to check.
+
+        Returns:
+            True if the deployment is healthy, False otherwise.
+        """
+        import requests
+
+        from zenml.enums import DeploymentDefaultEndpoints
+
+        assert deployment.snapshot, "Deployment snapshot not found"
+
+        settings = (
+            deployment.snapshot.pipeline_configuration.deployment_settings
+        )
+
+        # If the health check endpoint is disabled, we consider the deployment healthy.
+        if (
+            DeploymentDefaultEndpoints.HEALTH
+            not in settings.include_default_endpoints
+        ):
+            logger.debug(
+                f"Health check disabled for deployment {deployment.name}"
+            )
+            return True
+
+        if not deployment.url:
+            logger.debug(
+                f"No URL available for deployment {deployment.name}, health check fails"
+            )
+            return False
+
+        health_check_path = f"{settings.root_url_path}{settings.api_url_path}{settings.health_url_path}"
+        health_check_url = f"{deployment.url}{health_check_path}"
+
+        logger.info(
+            f"Checking health endpoint for deployment {deployment.name}: {health_check_url}"
+        )
+
+        # Attempt to connect to the deployment and check if it is healthy
+        try:
+            response = requests.get(health_check_url, timeout=3)
+            if response.status_code == 200:
+                logger.info(
+                    f"Health check passed for deployment {deployment.name}"
+                )
+                return True
+            else:
+                logger.warning(
+                    f"Health check endpoint for deployment '{deployment.name}' "
+                    f"at '{health_check_url}' returned status code "
+                    f"{response.status_code}"
+                )
+                return False
+        except Exception as e:
+            logger.warning(
+                f"Health check endpoint for deployment '{deployment.name}' "
+                f"at '{health_check_url}' is not reachable: {e}"
+            )
+            return False
+
     def do_get_deployment_state_logs(
         self,
         deployment: DeploymentResponse,