#266 UI: Implement Workflow Replay Capability

Add replay/time-travel debugging UI for completed workflows. ## API Endpoints Available - GET /api/v1/workflows/{workflow_run_id}/replay/simulate - Simulate workflow execution - GET /api/v1/workflows/{workflow_run_id}/replay/data - Get raw replay data (checkpoints, events) ## Implementation Steps ### Phase 1: Replay Button & Basic View 1. Add 'Replay' button to workflow detail page (only for completed/failed workflows) 2. Create /workflows/{id}/replay route 3. Call /replay/simulate endpoint and display simulation_status (success/failed) 4. Show executed_steps list with timing from replay_logs ### Phase 2: Timeline Visualization 1. Parse replay_logs array to build execution timeline 2. Display tasks as nodes with status icons (✅ success, ❌ failed) 3. Show task duration from timing data (e.g., 'setup_directory (38.95ms)') 4. Highlight divergences if any (divergences array) ### Phase 3: Variable Inspector 1. Parse SetVariable/GetVariable entries from replay_logs 2. Build collapsible tree view of variables at each step 3. Show variable values with JSON syntax highlighting 4. Filter by variable name ### Phase 4: Checkpoint Browser 1. Display checkpoints_available count 2. If checkpoints exist, allow browsing checkpoint data 3. Show which checkpoints were used during simulation ### Phase 5: Divergence Detection 1. If divergence_count > 0, show warning banner 2. List each divergence with expected vs actual values 3. Highlight affected tasks in timeline ## Response Schema (from /replay/simulate) ```json { "simulation_status": "success|failed", "workflow_name": "string", "executed_steps": ["task1", "task2"], "steps_executed_count": 6, "checkpoints_available": 0, "divergences": [], "replay_logs": ["✅ [task_name] (timing) → result..."], "error": null | {"error_type", "error_message", "error_traceback"} } ``` ## UI Components Needed - ReplayButton component - ReplayTimeline component - VariableInspector component - DivergenceAlert component - CheckpointBrowser component