docs: add VitePress documentation site

- 22 content pages across Guide, Concepts, and Reference sections
- Custom indigo/cyan theme with Lucide icons and Mermaid diagrams
- GitHub Actions workflow for GitHub Pages deployment
- Live preview: https://mempalace-docs.netlify.app/

.github/workflows/deploy-docs.yml

@@ -0,0 +1,52 @@
+name: Deploy Docs
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'website/**'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Install dependencies
+        working-directory: website
+        run: bun install
+
+      - name: Build docs
+        working-directory: website
+        run: bun run docs:build
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: website/.vitepress/dist
+
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4