fix: apply JumpStart model spec enable_network_isolation in ModelBuilder

In v2, JumpStart models deployed with EnableNetworkIsolation=True because
the JumpStartModel class read inference_enable_network_isolation from the
model spec JSON. In v3's ModelBuilder, this field was never extracted from
the JumpStart init_kwargs or deploy_kwargs, causing all JumpStart models
to deploy without network isolation (defaulting to False).

This fix applies enable_network_isolation from the JumpStart model spec
in both code paths:
1. _build_for_jumpstart() - regular build path via get_init_kwargs()
2. from_jumpstart_config() - classmethod path via _retrieve_model_deploy_kwargs()

The user-provided value (via network= param) takes precedence.

Author: lnealrei

sagemaker-serve/src/sagemaker/serve/model_builder.py

@@ -3621,6 +3621,12 @@ def from_jumpstart_config(
         )
         mb_instance.inference_ami_version = deploy_kwargs.get("inference_ami_version")
 
+        # Apply network isolation from JumpStart model spec if not set by user via network param
+        if not mb_instance._enable_network_isolation and deploy_kwargs.get(
+            "enable_network_isolation"
+        ):
+            mb_instance._enable_network_isolation = deploy_kwargs["enable_network_isolation"]
+
         return mb_instance
 
     @_telemetry_emitter(feature=Feature.MODEL_CUSTOMIZATION, func_name="model_builder.transformer")

sagemaker-serve/src/sagemaker/serve/model_builder_servers.py

@@ -877,6 +877,13 @@ def _build_for_jumpstart(self) -> Model:
         if hasattr(init_kwargs, "env") and init_kwargs.env:
             self.env_vars.update(init_kwargs.env)
 
+        # Apply network isolation from JumpStart model spec if not already set by user
+        if (
+            not self._enable_network_isolation
+            and getattr(init_kwargs, "enable_network_isolation", None) is not None
+        ):
+            self._enable_network_isolation = init_kwargs.enable_network_isolation
+
         # Handle model artifacts for fine-tuned models
         if hasattr(init_kwargs, "model_data") and init_kwargs.model_data:
             if (