#265 ReplayContext simulation fails on completed workflows

Two bugs in ReplayContext that caused simulation to fail on completed workflows: 1) get_executed_tasks() returned historical tasks (executed_steps) instead of runtime tracking set, causing 'no starting tasks' error 2) report_progress() used _metadata instead of metadata, mismatching DurableContext signature Fixed by: - Renamed executed_tasks to _runtime_executed_tasks (separate from executed_steps) - Changed _metadata to metadata in report_progress() Files: engine/replay/replay_context.py