docs(learning-hub): sync cli-for-beginners with upstream v1.0.61-62 changes (#2059)

- Chapter 01: Add /settings to Agent Environment slash commands table
- Chapter 01: Add /app to Help and Feedback slash commands table
- Chapter 04: Add ~/.copilot/instructions/**/*.instructions.md user-level
  instruction file location to Instruction File Formats table
- Chapter 06: Update MCP Configuration File section to mention .github/mcp.json
  as a new workspace-level config location (auto-loaded alongside .mcp.json)
- Chapter 06: Add deprecation note for .vscode/mcp.json (no longer supported)
- Chapter 06: Update 'Save this as...' line and troubleshooting table to use
  .mcp.json instead of .vscode/mcp.json for project-level config
- Bump lastUpdated frontmatter on all three changed pages to 2026-06-19

Upstream commits:
- a6ab44b08fa5 docs: add /settings, /app commands and new config locations from v1.0.61-62
- 05493b8b493b Update README.md (06-mcp-servers)
- 53326395c92a Merge pull request #165 (bot sync)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

website/src/content/docs/learning-hub/cli-for-beginners/01-setup-and-first-steps.md

@@ -3,7 +3,7 @@ title: '01 · First Steps'
 description: 'Experience your first GitHub Copilot CLI demos and learn the three main interaction modes.'
 authors:
   - GitHub Copilot Learning Hub Team
-lastUpdated: 2026-03-20
+lastUpdated: 2026-06-19
 ---
 
 ![Chapter 01: First Steps](/images/learning-hub/copilot-cli-for-beginners/01/chapter-header.png)
@@ -393,6 +393,7 @@ That's it for getting started! As you become comfortable, you can explore additi
 | `/agent` | Browse and select from available agents |
 | `/skills` | Manage skills for enhanced capabilities |
 | `/mcp` | Manage MCP server configuration |
+| `/settings` | Open an interactive dialog to browse and edit all user settings in one place |
 
 > 💡 Skills are covered in detail in [Chapter 05](../05-skills/). MCP servers are covered in [Chapter 06](../06-mcp-servers/).
 
@@ -442,6 +443,7 @@ That's it for getting started! As you become comfortable, you can explore additi
 
 | Command | What It Does |
 |---------|--------------|
+| `/app` | Open the GitHub app (or browser fallback) directly from the CLI |
 | `/help` | Show all available commands |
 | `/changelog` | Display changelog for CLI versions |
 | `/feedback` | Submit feedback to GitHub |