feat(ui): elevate workstation design with Stitch Precision Engineering aesthetics

- establish root DESIGN.md and Blueprint Indigo (#5e6ad2) palette, eliminating pure black and em-dashes
- redesign left panel job list into high-density linear items with tactile micro-action docks
- refactor center 3D viewport controls into frosted grouped floating HUD dock with integrated BBOX telemetry
- upgrade right inspector sub-panels (Spec, Validation, Code, History) to property grids and eliminate card-soup
- introduce PanelErrorBoundary fault isolation and ergonomic empty states