Summary

Replace std::this_thread::sleep_for with deterministic event-based synchronization primitives to eliminate test flakiness.

Background

The current test suite relies on time-based waits (e.g., sleep_for(100ms)). This causes two major issues:

1. Flakiness: Tests fail on busy CI runners if the operation takes longer than the hardcoded wait time.
2. Slowness: Tests wait longer than necessary (e.g., waiting 100ms for an operation that takes 1ms).

Tasks

Refactor the following files to use std::promise/future, std::condition_variable, or std::latch:

• integration_tests/failures/error_handling_test.cpp
• integration_tests/framework/test_helpers.h
• integration_tests/scenarios/event_bus_integration_test.cpp
• integration_tests/scenarios/full_system_integration_test.cpp
• integration_tests/scenarios/runtime_binding_integration_test.cpp
• integration_tests/stress/stress_test.cpp
• tests/config_watcher_test.cpp
• tests/event_bus_failure_test.cpp
• tests/executor_test.cpp
• tests/global_logger_registry_test.cpp
• tests/improved_event_bus_test.cpp
• tests/thread_safety_tests.cpp
• tests/unified_bootstrapper_test.cpp

Acceptance Criteria

• All sleep_for usage in test logic is replaced with synchronization primitives.
• Tests pass consistently with --gtest_repeat=100.
• No arbitrary duration constants remain in the synchronization logic (timeouts are allowed for failure safety, but not for control flow).