feat(backend): add v2 LLM validation fields to health service

- DashboardHealthItem schema: add run_id, policy_id, execution_path,
  issues_count, timings, token_usage, screenshot_paths, chunk_count,
  dashboard_name fields for v2 LLM validation reporting.
- HealthService: populate v2 fields from validation run records.
- ValidationService: update to support v2 validation run fields.
- validation_tasks route: minor fix for v2 field handling.
- tailwind.config.js: refactor design tokens — add success/warning/info
  palettes, surface/border/text hierarchy, semantic action colors.
- Agent configs: update svelte-coder and semantics-svelte for
  .svelte.ts runes and Screen Model patterns.

.opencode/agents/svelte-coder.md

@@ -48,13 +48,14 @@ See `semantics-core` §VI for the canonical tool reference. For Svelte frontend
 ## ss-tools Frontend Scope
 You own:
 - SvelteKit routes (`frontend/src/routes/`)
-- Svelte 5 components (`frontend/src/lib/components/`)
+- Svelte 5 components (`frontend/src/lib/components/` — **only directory for NEW domain components**)
+- **UI atoms** (`frontend/src/lib/ui/` — Button, Card, Input, Select, PageHeader, Icon, HelpTooltip, LanguageSwitcher)
 - **Screen Models** (`frontend/src/lib/models/` — `[TYPE Model]` contracts for screen-level state)
 - Svelte stores (`frontend/src/lib/stores/`)
 - API client layer (`frontend/src/lib/api/`)
 - i18n localization (`frontend/src/i18n/`)
 - Pages, layouts, and services
-- Tailwind-first UI implementation
+- Tailwind-first UI implementation (semantic tokens ONLY — no raw blue-600, gray-*, indigo-*)
 - UX state repair and route-level behavior
 - Browser-driven acceptance for frontend scenarios
 - Screenshot and console-driven debugging
@@ -64,6 +65,9 @@ You do not own:
 - Backend-only implementation unless explicitly scoped
 - Semantic repair outside the frontend boundary unless required by the UI change
 
+### Frozen zones (LEGACY — migrate away, do NOT add)
+- `frontend/src/components/` — legacy component directory. **Do not create new files here.** All new domain components go in `lib/components/<domain>/`.
+
 ## Required Workflow
 1. **Discover or create the Model first.** For any screen with cross-widget state:
    - grep `@semantics.*<keyword>` across `frontend/src/` to find existing models
@@ -107,13 +111,25 @@ For frontend design and implementation tasks, default to these rules unless the
 - Prefer whitespace, alignment, scale, and contrast before adding chrome.
 - Default to cardless layouts; use cards only when a card is the actual interaction container for a specific resource (Dashboard, Dataset, Task).
 
-### Visual system (ss-tools design tokens)
-- Primary: `blue-600` / `blue-700` (buttons, links, accents)
-- Success: `green-500` / `green-600`
-- Error: `red-500` / `red-600`
-- Warning: `amber-400` / `amber-500`
-- Background: `gray-50` (page), `white` (cards/surfaces)
-- Text: `gray-900` (primary), `gray-500` (muted)
+### Visual system (ss-tools design tokens — source: `tailwind.config.js`)
+**Raw Tailwind colors (`blue-600`, `green-500`, `red-600`, `gray-*`, `indigo-*`) are DEPRECATED in page and component code.** Use ONLY these semantic tokens:
+
+- Primary action: `bg-primary text-white hover:bg-primary-hover` (maps to blue-600/700)
+- Destructive action / error: `bg-destructive text-white`, `bg-destructive-light text-destructive border-destructive-ring`
+- Page background: `bg-surface-page`
+- Card surface: `bg-surface-card`
+- Muted surface: `bg-surface-muted`
+- Default border: `border-border`; strong border (inputs): `border-border-strong`
+- Primary text: `text-text`; muted text: `text-text-muted`; subtle text (placeholders): `text-text-subtle`
+- Success: `text-success bg-success-light border-success-*`
+- Warning: `text-warning bg-warning-light border-warning-*`
+- Info: `text-info bg-info-light border-info-*`
+
+### UI component reuse (MANDATORY)
+- **Page-level UI MUST use `$lib/ui` atoms:** `<Button>`, `<Card>`, `<Input>`, `<Select>`, `<PageHeader>`. Raw `<button>` and manual `<div class="bg-white rounded...">` in page files is a violation unless there is a documented exception.
+- **`src/components/` is LEGACY FROZEN.** Do not create new files there. Do not extend it. New domain components go in `src/lib/components/<domain>/`.
+- **`migration/+page.svelte`** is the state architecture reference (model-first with thin component) but NOT the visual reference — it still has legacy raw colors and manual buttons. Use the canonical template in `semantics-svelte` §VI for visual patterns.
+- **Button variant naming:** Use `"destructive"` (canonical). `"danger"` is a deprecated alias — prefer `"destructive"`.
 
 ### ss-tools specific pages
 - **Dashboard Hub** — Git-tracked dashboards with status badges