#223 API: Add missing replay and workflow state endpoints

## Problem Several Phase 1-3 replay features were implemented in CLI but not exposed via API. ## Missing API Support ### 1. Simulate API missing --resume-from (Issue #217) **CLI has:** hwe replay --simulate --resume-from STEP_NAME **API needs:** POST /workflows/{id}/simulate should accept resume_from body parameter ### 2. Replay API missing --include-children (Issue #221) **CLI has:** hwe replay --include-children **API needs:** GET /workflows/{id}/replay?include_children=true should return workflow tree ### 3. Replay API missing --list-steps (Issue #217) **CLI has:** hwe replay --list-steps **API needs:** GET /workflows/{id}/replay/steps endpoint to list checkpointed steps ### 4. Variable query missing version info (Issue #222) **Current:** GET /query/{id}/variables returns value only **Needs:** Return {value, version} for optimistic locking support ### 5. No lock history endpoint (Issue #218) **Needs:** GET /workflows/{id}/locks to view lock_acquired/lock_released events ### 6. No saga/compensation history endpoint (Issue #214) **Needs:** GET /workflows/{id}/sagas to view saga_started/compensation events ## Affected Issues #214, #217, #218, #221, #222 ## Implementation Notes - replay.py already has /replay and /simulate endpoints - extend them - queries.py has variable query - add version field - New endpoints needed for locks and sagas ## Effort: Medium