Add optional title field to server.json schema (#608)

## Summary

Introduces a new optional `title` field for MCP servers to provide a
clean, human-readable display name that clients and subregistries can
use for display purposes.

Fixes #606

## Changes

- Added `title` field to `ServerJSON` type (optional, max 100 chars)
- Added validation to reject titles ending with 'MCP Server', 'MCP
server', or 'MCP' suffixes
- Updated JSON schema and OpenAPI specification
- Added comprehensive test coverage for title validation
- Updated all documentation examples to demonstrate the new field

## Validation

The title field:
- Is optional (can be omitted)
- Must not be only whitespace if provided
- Must not end with MCP-related suffixes (case-insensitive)
- Can contain 'MCP' in the middle (e.g., "MCP Weather API" is valid)

Examples:
- ✅ Valid: "GitHub", "Weather API", "Slack Integration"
- ❌ Invalid: "GitHub MCP", "Weather MCP Server", "Slack-MCP"

---------

Co-authored-by: Claude <noreply@anthropic.com>

docs/reference/api/openapi.yaml

@@ -156,6 +156,7 @@ paths:
                 value:
                   name: "io.modelcontextprotocol/filesystem"
                   description: "Node.js server implementing Model Context Protocol (MCP) for filesystem operations."
+                  title: "Filesystem"
                   repository:
                     url: "https://github.com/modelcontextprotocol/servers"
                     source: "github"
@@ -177,6 +178,7 @@ paths:
                 value:
                   name: "com.example/demo-server"
                   description: "Example MCP server demonstrating publisher extensions."
+                  title: "Demo Server"
                   repository:
                     url: "https://github.com/example/mcp-demo"
                     source: "github"
@@ -267,7 +269,6 @@ components:
           description: "Optional relative path from repository root to the server location within a monorepo structure"
           example: "src/everything"
 
-
     ServerList:
       type: object
       required:
@@ -502,6 +503,10 @@ components:
           type: string
           description: "Human-readable description of the server's functionality"
           example: "Node.js server implementing Model Context Protocol (MCP) for filesystem operations."
+        title:
+          type: string
+          description: "Optional human-readable title or display name for the MCP server. MCP subregistries or clients MAY choose to use this for display purposes."
+          example: "Filesystem"
         repository:
           $ref: '#/components/schemas/Repository'
         version: