Create shared DataOps design system and component tokens

[alexeygrigorev]

Goal

Create a shared design system for the unified DataOps portal so the docs portal, task workflows, and podcast assistant UI use the same visual language instead of drifting into separate sites/tools.

Context

There has already been work to make the related surfaces feel as close as possible. This issue should preserve that work, define the shared foundation, and make the UI degrade smoothly across desktop, tablet, and mobile.

Scope

• Define design tokens for color, typography, spacing, borders, focus states, shadows, and layout density.
• Define reusable component primitives for navigation, sidebars, page headers, forms, filters, tables/lists, empty states, modals, command/search, document cards, task rows, status badges, and assistant job panels.
• Map existing docs portal UI pieces and DataTasks UI pieces to the shared component set.
• Identify which components can be implemented as plain HTML/CSS/JS first and which need a future frontend framework decision.
• Create a migration plan that keeps v1 usable while components are replaced incrementally.
• Include responsive rules and graceful degradation behavior for narrow screens and lower-capability browsers.

Acceptance Criteria

• A design-system spec exists in _docs/ or docs/ with tokens, component inventory, and usage rules.
• Existing docs portal and task-engine surfaces are audited against the component inventory.
• The spec includes mobile and desktop responsive behavior for core layouts.
• At least one concrete implementation issue is linked for applying the first shared components to the v1 portal shell.
• The design system avoids introducing a second visual language for podcast assistant or task workflows.