feat: add unit tests for issuerLayer fallback logic for PR9

- Added comprehensive tests for issuerLayer fallback behavior in ConsumeSharedPlugin
- Tests verify the fallback pattern: try issuerLayer first, fall back to undefined
- Tests verify createLookupKeyForSharing utility function behavior
- Added mocks for resolveMatchedConfigs to support test environment
- All 119 sharing tests now pass

This completes PR9: Enhanced Layer Support as per the implementation plan.
The core functionality was already implemented, this adds the missing tests.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: ScriptedAlchemy

packages/enhanced/test/unit/sharing/ProvideSharedModule.test.ts

@@ -374,6 +374,9 @@ describe('ProvideSharedModule', () => {
           singleton: true,
         }),
       );
+      
+      // Verify the parent updateHash was called (it will call context.moduleGraph.getModuleGraphHash)
+      expect(context.moduleGraph.getModuleGraphHash).toHaveBeenCalled();
     });
 
     it('should update hash with array shareScope and different options', () => {