fix(packages): resolve typecheck failures in button tests and cast feature

- Add missing `available` field to test helpers for FullscreenButtonState and PiPButtonState
- Pass `media` argument to `exitFullscreen()` in cast feature (signature changed)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mihar-22

packages/core/src/core/ui/fullscreen-button/tests/fullscreen-button-core.test.ts

@@ -19,6 +19,7 @@ function createState(overrides: Partial<FullscreenButtonState> = {}): Fullscreen
   return {
     fullscreen: false,
     availability: 'available',
+    available: true,
     label: '',
     ...overrides,
   };

packages/core/src/core/ui/pip-button/tests/pip-button-core.test.ts

@@ -19,6 +19,7 @@ function createState(overrides: Partial<PiPButtonState> = {}): PiPButtonState {
   return {
     pip: false,
     availability: 'available',
+    available: true,
     label: '',
     ...overrides,
   };

packages/core/src/dom/store/features/cast.ts

@@ -20,7 +20,7 @@ export const castFeature = definePlayerFeature({
       }
 
       if (isFullscreenElement(container, media)) {
-        await exitFullscreen();
+        await exitFullscreen(media);
       }
 
       return requestCast(media);