Add framework for conceptual docs

docs/concepts/index.md

@@ -0,0 +1,2 @@
+
+Welcome to the conceptual documentation for the Model Context Protocol SDK. Here you'll find high-level overviews, explanations, and guides to help you understand how the SDK implements the Model Context Protocol.

docs/concepts/toc.yml

@@ -0,0 +1,5 @@
+items:
+- name: Overview
+  href: index.md
+- name: Elicitation
+  uid: elicitation

docs/docfx.json

@@ -42,6 +42,7 @@
       "_appLogoPath": "images/mcp.svg",
       "_appFaviconPath": "images/favicon.ico",
       "_enableSearch": true,
+      "_appFooter": "<script>(function(){var el=document.querySelector('.next-article');if(el)el.style.display='none';})();</script>",
       "pdf": false
     }
   }

docs/toc.yml

@@ -1,5 +1,7 @@
 items:
-- name: API Docs
+- name: Documentation
+  href: concepts/index.md
+- name: API Reference
   href: api/ModelContextProtocol.yml
 - name: Github
   href: https://github.com/ModelContextProtocol/csharp-sdk