Update client authentication support section

Revise the "Client support for MCP server authentication" section to
reflect the current state of the MCP ecosystem more accurately:

- Remove outdated claim that "most clients do not support authentication"
- Acknowledge that authentication support varies across clients
- Simplify guidance to recommend looking for clients that support MCP
  authentication standards (OAuth 2.1 and transport-level auth)
- Remove redundant use cases section (already covered elsewhere in docs)
- Remove "Expected evolution" and "Planning for the future" subsections

The revised section is more concise and reflects that while authentication
support is not universal, many clients now support it to varying degrees.

Author: jhrozek

docs/toolhive/concepts/auth-framework.mdx

@@ -217,52 +217,25 @@ benefits:
 ## Client support for MCP server authentication
 
 While ToolHive provides a robust authentication and authorization framework for
-MCP servers, it's important to understand the current state of client support
-across the ecosystem.
+MCP servers, it's important to understand that authentication support varies
+across the MCP client ecosystem.
 
-### Current limitations
+### Current state of client support
 
-Most AI coding clients and MCP client implementations do not currently support
-authentication when connecting to MCP servers. This means that many popular AI
-development tools expect MCP servers to be accessible without authentication,
-which limits the security options available for production deployments.
+The MCP ecosystem includes numerous clients with varying levels of
+authentication support. However, authentication support is not universal. Some
+clients focus primarily on local, unauthenticated MCP servers for development
+workflows, while others provide enterprise-grade authentication for production
+deployments.
 
-### Expected evolution
+When selecting an MCP client for authenticated workflows, look for clients that
+support the MCP authentication standards, including OAuth 2.1 and
+transport-level authentication mechanisms.
 
-As the official MCP specification matures and security becomes a higher priority
-for production MCP deployments, we expect to see authentication support
-implemented across major AI coding clients. The MCP specification already
-includes provisions for OAuth 2.1-based authorization, and client
-implementations are likely to adopt these standards over time.
-
-### Current use cases
-
-Today, MCP server authentication is primarily valuable for:
-
-- **Custom AI applications and agent workflows:** If you're building your own AI
-  application or agent system, you can implement MCP client authentication to
-  work with ToolHive's secure MCP servers.
-- **Kubernetes service account authentication:** For automated services running
-  in Kubernetes clusters, service account tokens provide a secure way to
-  authenticate with MCP servers without requiring interactive login flows.
-- **Internal tooling and APIs:** Organizations building internal tools that
-  consume MCP servers can implement authentication to secure access to sensitive
-  resources and tools.
-
-### Planning for the future
-
-When designing your MCP server security strategy, consider that:
-
-- Authentication support in popular AI coding clients will likely improve over
-  time
-- ToolHive's OIDC-based approach aligns with emerging standards and will be
-  compatible with future client implementations
-- You can start with authenticated MCP servers for internal use cases and
-  gradually expand as client support improves
-
-This evolving landscape means that while authentication capabilities exist
-today, their practical application depends on your specific use case and client
-requirements.
+ToolHive's OIDC-based authentication approach aligns with industry standards and
+works with clients that support modern authentication protocols. As the MCP
+ecosystem continues to mature, we expect authentication support to become more
+standardized across clients.
 
 ## Related information