Remove previewFeatures and default to Gemini 3 (#18414)

packages/core/src/availability/fallbackIntegration.test.ts

@@ -27,7 +27,6 @@ describe('Fallback Integration', () => {
       getModel: () => PREVIEW_GEMINI_MODEL_AUTO,
       getActiveModel: () => PREVIEW_GEMINI_MODEL_AUTO,
       setActiveModel: vi.fn(),
-      getPreviewFeatures: () => true, // Preview enabled for Gemini 3
       getUserTier: () => undefined,
       getModelAvailabilityService: () => availabilityService,
       modelConfigService: undefined as unknown as ModelConfigService,

packages/core/src/availability/policyHelpers.test.ts

@@ -19,7 +19,6 @@ import {
 
 const createMockConfig = (overrides: Partial<Config> = {}): Config =>
   ({
-    getPreviewFeatures: () => false,
     getUserTier: () => undefined,
     getModel: () => 'gemini-2.5-pro',
     ...overrides,