test: mock Unix platform for SIGTERM behavior in ClaudeUsageService tests

Added a mock for the Unix platform in the SIGTERM test case to ensure proper behavior during testing on non-Windows systems. This change enhances the reliability of the tests by simulating the expected environment for process termination.

apps/server/tests/unit/services/claude-usage-service.test.ts

@@ -586,6 +586,8 @@ Resets in 2h
 
     it('should send SIGTERM after ESC if process does not exit', async () => {
       vi.useFakeTimers();
+      // Mock Unix platform to test SIGTERM behavior (Windows calls kill() without signal)
+      vi.mocked(os.platform).mockReturnValue('darwin');
       const ptyService = new ClaudeUsageService();
 
       let dataCallback: Function | undefined;