fix: resolve all remaining test failures and improve test reliability

- Fix clear-subtasks test by implementing deep copy of mock data to prevent mutation issues between tests
- Fix add-task test by uncommenting and properly configuring generateTaskFiles call with correct parameters
- Fix analyze-task-complexity tests by properly mocking fs.writeFileSync with shared mock function
- Update test expectations to match actual function signatures and data structures
- Improve mock setup consistency across all test suites
- Ensure all tests now pass (329 total: 318 passed, 11 skipped, 0 failed)

.taskmaster/reports/task-complexity-report_test-prd-tag.json

@@ -50,4 +50,4 @@
 			"reasoning": "This task requires simultaneous development of multiple features, integration with CLI, and comprehensive testing. The coordination and depth required for both implementation and validation make it the most complex among the listed tasks."
 		}
 	]
-}
+}