Debug mode

The Debug Mode feature allows users to interactively step through their query → transform pipeline by dragging a visual "debug line" to enable/disable queries and transformations. This was completed as part of the hackathon, but the logic, architecture, and overall implementation need refinement. Debug mode adds an interactive debugging experience to the panel editor: - Visual Debug Line: A draggable horizontal line in the query/transform list - Interactive Stepping: Drag the line to enable/disable pipeline steps - State Preview: See what data looks like at each step of the pipeline - Toggle Button: Bug icon in the Pipeline header to enter/exit debug mode ### 📁 Implementation files in hackathon branch - useDebugMode.ts (138 lines) - Custom hook managing debug UI state - debugModeHelpers.ts (109 lines) - Utilities for state sync/restore - QueryTransformList.tsx (integration) - Main component with debug line rendering - PanelDataPane.tsx - State management for debug position ### Current known issues - State management and state synchronization are **FRAGILE** - Position calculations need to be refined and hardened - Needs tests ❗ ### Acceptance Criteria - [ ] State restoration works correctly after reordering items in a non-hacky way - [ ] Integration tests added and passing - [ ] Hardcoded dimensions removed or documented - [ ] Error boundary added - [ ] Manual testing with 20+ queries/transforms - [ ] Documentation updated with debug mode usage