Update .NET AI ecosystem article to use current Foundry product names

[Copilot]

The .NET + AI ecosystem tools and SDKs article still used older Foundry product names in headings, summary guidance, and explanatory text. This update aligns the page with the current naming for Microsoft Foundry and Foundry Toolkit.

• Terminology updates

  • Replaced Azure AI Foundry with Microsoft Foundry
  • Replaced AI Toolkit with Foundry Toolkit

• Navigation consistency

  • Updated section headings and internal anchor links to match the renamed products
  • Updated summary examples and recommendation table entries so references stay consistent across the page

• Article metadata

  • Added the required ai-usage frontmatter entry for the AI-assisted documentation edit

- **Enterprise cloud app**: MEAI + Microsoft Foundry + Aspire
- **Local-first app**: MEAI + Foundry Local + Foundry Toolkit (development)

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Internal previews

📄 File	🔗 Preview link
docs/ai/dotnet-ai-ecosystem.md	docs/ai/dotnet-ai-ecosystem

[gewarren]

cc @alvinashcraft

[Copilot]

Pull request overview

This PR updates the .NET + AI ecosystem tools and SDKs article to reflect current product naming, aligning headings, internal anchor links, and guidance text with “Microsoft Foundry” and “Foundry Toolkit,” and adds the required AI-usage metadata.

Changes:

• Replaced “Azure AI Foundry” with “Microsoft Foundry” throughout the article, including the section heading and internal links.
• Replaced “AI Toolkit” with “Foundry Toolkit” throughout the article, including the section heading and internal links.
• Added ai-usage: ai-assisted frontmatter metadata.