feat(website): add samples/cookbook page with recipe browser

Integrates the cookbook/ folder into the website's Samples page:

Data Structure:
- Add cookbook/cookbook.yml manifest defining cookbooks and recipes
- Add .schemas/cookbook.schema.json for validation
- Add COOKBOOK_DIR constant to eng/constants.mjs

Build Integration:
- Add generateSamplesData() to generate samples.json from cookbook.yml
- Include recipe variants with file paths for each language
- Add samples count to manifest.json

Website UI:
- Create samples.ts with FuzzySearch, language/tag filtering
- Replace placeholder samples.astro with functional recipe browser
- Recipe cards with language indicators and action buttons
- Language tabs for switching between implementations
- View Recipe/View Example buttons open modal
- GitHub link for each recipe

Features:
- Search recipes by name/description
- Filter by programming language (Node.js, Python, .NET, Go)
- Filter by tags (multi-select with Choices.js)
- 5 recipes across 4 languages = 20 recipe variants

cookbook/cookbook.yml

@@ -0,0 +1,63 @@
+# yaml-language-server: $schema=../.schemas/cookbook.schema.json
+# Cookbook manifest for the Awesome GitHub Copilot website
+# This file defines the structure of cookbooks and recipes for the Samples page
+
+cookbooks:
+  - id: copilot-sdk
+    name: GitHub Copilot SDK
+    description: Ready-to-use recipes for building with the GitHub Copilot SDK across multiple languages
+    path: cookbook/copilot-sdk
+    featured: true
+    languages:
+      - id: nodejs
+        name: Node.js / TypeScript
+        icon: 🟢
+        extension: .ts
+      - id: python
+        name: Python
+        icon: 🐍
+        extension: .py
+      - id: dotnet
+        name: .NET (C#)
+        icon: 🟣
+        extension: .cs
+      - id: go
+        name: Go
+        icon: 🔵
+        extension: .go
+    recipes:
+      - id: error-handling
+        name: Error Handling
+        description: Handle errors gracefully including connection failures, timeouts, and cleanup
+        tags:
+          - errors
+          - basics
+          - reliability
+      - id: multiple-sessions
+        name: Multiple Sessions
+        description: Manage multiple independent conversations simultaneously
+        tags:
+          - sessions
+          - advanced
+          - concurrency
+      - id: managing-local-files
+        name: Managing Local Files
+        description: Organize files by metadata using AI-powered grouping strategies
+        tags:
+          - files
+          - organization
+          - ai-powered
+      - id: pr-visualization
+        name: PR Visualization
+        description: Generate interactive PR age charts using GitHub MCP Server
+        tags:
+          - github
+          - visualization
+          - mcp
+      - id: persisting-sessions
+        name: Persisting Sessions
+        description: Save and resume sessions across restarts
+        tags:
+          - sessions
+          - persistence
+          - state-management