fix: Dockerfile stub binary not replaced, design system rules

- remove stub colony binary after dep cache so cargo rebuilds with real source
- expand .claude/rules/frontend.md with full design system enforcement
- mandatory: semantic tokens, shadcn components, Tailwind only, mobile-first
- forbidden: inline styles, custom CSS, arbitrary colors, raw HTML elements

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/rules/frontend.md

@@ -3,4 +3,42 @@ paths:
   - "ui/**"
 ---
 
-When working on frontend code, always use the `/frontend-design` skill for component design, layout decisions, and UI implementation.
+## Design System Rules
+
+**Stack:** React + Tailwind CSS + shadcn/ui. No exceptions.
+
+**Use the `/frontend-design` skill** for all component design and layout decisions.
+
+### Mandatory
+- All styling via Tailwind utility classes
+- Use shadcn/ui components from `@/components/ui/` — run `npx shadcn@latest add <component>` to install new ones
+- Use semantic color tokens: `bg-background`, `text-foreground`, `bg-card`, `text-muted-foreground`, `border-border`, etc.
+- Use theme spacing: Tailwind's default scale (p-2, p-3, p-4, gap-2, etc.)
+- Mobile-first: base classes for mobile, `md:` for desktop overrides
+- Touch targets: min 44px on mobile (`min-h-[44px] min-w-[44px]`)
+- Use `cn()` from `@/lib/utils` for conditional classes
+
+### Forbidden
+- No `style={}` JSX props
+- No `<style>` tags
+- No `.css` files (except index.css theme config)
+- No arbitrary color values like `bg-[#xxx]` or `bg-[oklch(...)]` — use semantic tokens or CSS variables via `bg-[var(--color-name)]`
+- No raw HTML elements when a shadcn component exists (use `<Button>` not `<button>`, `<Input>` not `<input>`)
+
+### Color Palette
+| Token | Use for |
+|-------|---------|
+| `bg-background` / `text-foreground` | Main content |
+| `bg-card` / `text-card-foreground` | Elevated surfaces |
+| `bg-muted` / `text-muted-foreground` | Subdued content |
+| `bg-primary` / `text-primary-foreground` | Primary actions |
+| `border-border` | All borders |
+| `text-emerald-500` | Result/success |
+| `text-red-500` / `text-red-400` | Errors |
+| `text-blue-500` / `text-blue-400` | Plans, agent accent |
+| `text-amber-500` | Code |
+
+### Adding shadcn components
+```bash
+cd ui/colony && npx shadcn@latest add <component-name>
+```