docs: import MCP Java and C# SDK tutorial packs

[johnxie]

Summary

Adds pack-bo with two official MCP SDK tracks:

• tutorials/mcp-java-sdk-tutorial/ (8 chapters + index)
  • Covers module boundaries, reactive architecture, transport strategy, security, conformance, and Spring integration.
• tutorials/mcp-csharp-sdk-tutorial/ (8 chapters + index)
  • Covers package selection, hosting and ASP.NET Core transport patterns, filters, advanced capabilities, protected server/client flows, diagnostics/versioning, and ops workflows.

Also refreshes core discoverability surfaces:

• README MCP path/catalog/stats updates
• categories/ai-ml-platforms.md MCP path + featured updates
• IMPORT_ROADMAP_TODO.md (pack-bn marked done; pack-bo added in progress)
• Regenerated tutorial/discoverability/status artifacts

Validation

• python3 scripts/docs_health.py --root . --baseline-file .github/baselines/broken-local-links.txt
• python3 scripts/check_index_format_v2.py --root .
• generator drift checks:
  • scripts/generate_tutorial_manifest.py
  • scripts/generate_discoverability_assets.py
  • scripts/update_tutorials_readme_snapshot.py
  • scripts/update_repo_status_docs.py
• outbound URL check for new index references

All checks passed.