docs: rename Overview tab to About MCP and move to last position (modelcontextprotocol#1317)

- Renamed /docs/overview directory to /docs/about
- Changed tab name from "Overview" to "About MCP"
- Moved tab from first position to last in navigation order
- Updated navigation reference from overview/index to about/index

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <[email protected]>

Author: jerryhong1

docs/overview/index.mdx docs/about/index.mdxdocs/overview/index.mdx renamed to docs/about/index.mdx

@@ -23,10 +23,6 @@
   "navigation": {
     "tabs": [
       {
-        "tab": "Overview",
-        "pages": ["overview/index"]
-      },
-        {
         "tab": "Documentation",
         "pages": [
           "docs/getting-started/intro",
@@ -284,6 +280,10 @@
           "clients",
           "examples"
         ]
+      },
+      {
+        "tab": "About MCP",
+        "pages": ["about/index"]
       }
     ]
   },