feat: add GitHub Pages deployment for development environment

- Creates unified build directory with portal at root
- Deploys all standard sites to subdirectories
- Configures for development environment (DOCS_ENV=development)
- Deploys to jonphipps.github.io/standards-dev
- Fixes 404 errors reported in post-deploy validation

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: jonphipps

.github/workflows/development-deploy.yml

@@ -0,0 +1,93 @@
+name: Development Deploy
+# Deploys to GitHub Pages for development environment testing
+# This runs on the development fork (jonphipps/standards-dev)
+
+on:
+  push:
+    branches: [dev]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+env:
+  HUSKY: 0
+  # Development environment configuration
+  DOCS_ENV: development
+  SITE_TITLE: IFLA Standards Portal (Development)
+  SITE_TAGLINE: International Federation of Library Associations and Institutions
+
+jobs:
+  build:
+    name: Build for Development Environment
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: 'pnpm'
+
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Build theme package
+        run: npx nx run @ifla/theme:build
+
+      - name: Build all sites for development
+        run: |
+          echo "🏗️ Building all sites for development environment..."
+          npx nx run-many --target=build --all --parallel=3
+          
+      - name: Create unified build directory
+        run: |
+          echo "📦 Creating unified build directory..."
+          mkdir -p _site
+          
+          # Copy portal to root
+          cp -r portal/build/* _site/
+          
+          # Copy each standard site to its subdirectory
+          for site in ISBDM LRM FRBR isbd muldicat unimarc newtest; do
+            if [ -d "standards/$site/build" ]; then
+              echo "Copying $site..."
+              mkdir -p "_site/$site"
+              cp -r "standards/$site/build/"* "_site/$site/"
+            fi
+          done
+          
+          echo "✅ Unified build created"
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ./_site
+
+  deploy:
+    name: Deploy to GitHub Pages
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4