Implement the 010-ui-baseline feature that establishes a modern UI using Tailwind CSS v4 and shadcn/ui-style components for the encounter screen

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

specs/010-ui-baseline/quickstart.md

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+# Quickstart: UI Baseline
+
+**Feature**: 010-ui-baseline | **Date**: 2026-03-05
+
+## Prerequisites
+
+- Node.js 18+
+- pnpm 10.6+
+
+## Setup
+
+```bash
+# Install dependencies (from repo root)
+pnpm install
+
+# Start dev server
+pnpm --filter web dev
+# → http://localhost:5173
+```
+
+## New Dependencies (to be added)
+
+```bash
+# Tailwind CSS v4 with Vite plugin
+pnpm --filter web add tailwindcss @tailwindcss/vite
+
+# shadcn/ui utilities
+pnpm --filter web add clsx tailwind-merge class-variance-authority
+
+# Radix UI primitives (used by shadcn/ui components)
+pnpm --filter web add @radix-ui/react-slot @radix-ui/react-tooltip
+
+# Icons
+pnpm --filter web add lucide-react
+```
+
+## Key Files
+
+| File | Purpose |
+|------|---------|
+| `apps/web/src/index.css` | Tailwind directives + CSS custom properties |
+| `apps/web/src/lib/utils.ts` | `cn()` class merge utility |
+| `apps/web/src/components/ui/` | shadcn/ui primitives (Button, Input, etc.) |
+| `apps/web/src/components/combatant-row.tsx` | Combatant row component |
+| `apps/web/src/App.tsx` | Main layout (header, list, action bar) |
+| `apps/web/vite.config.ts` | Updated with Tailwind plugin |
+
+## Quality Gate
+
+```bash
+# Must pass before commit
+pnpm check
+```
+
+This runs: knip → format → lint → typecheck → test
+
+## Design System
+
+- **Styling**: Tailwind CSS v4 utility classes
+- **Components**: shadcn/ui (copied into project, not a package dependency)
+- **Icons**: Lucide React
+- **Class merging**: `cn()` from `lib/utils.ts` (clsx + tailwind-merge)