feat(FN-4650): complete Step 1 — add sandbox experimental helper

Fusion-Task-Id: FN-4650
Fusion-Task-Lineage: 3da8db80-236b-46f6-8122-644abda35ca3

packages/core/src/__tests__/sandbox-settings.test.ts

@@ -5,6 +5,7 @@ import {
   PROJECT_SETTINGS_KEYS,
   SANDBOX_BACKEND_NAMES,
   SANDBOX_FAILURE_MODES,
+  isSandboxExperimentalEnabled,
   validateSandboxBackendName,
   validateSandboxFailureMode,
   validateSandboxPolicy,
@@ -102,4 +103,22 @@ describe("sandbox settings", () => {
       expect(validateSandboxProjectSettings("nope")).toBeUndefined();
     });
   });
+
+  describe("isSandboxExperimentalEnabled", () => {
+    it("returns false for undefined settings", () => {
+      expect(isSandboxExperimentalEnabled(undefined)).toBe(false);
+    });
+
+    it("returns false when sandbox flag is missing", () => {
+      expect(isSandboxExperimentalEnabled({ experimentalFeatures: {} })).toBe(false);
+    });
+
+    it("returns false when sandbox flag is false", () => {
+      expect(isSandboxExperimentalEnabled({ experimentalFeatures: { sandbox: false } })).toBe(false);
+    });
+
+    it("returns true when sandbox flag is true", () => {
+      expect(isSandboxExperimentalEnabled({ experimentalFeatures: { sandbox: true } })).toBe(true);
+    });
+  });
 });