Replace duplicate "Why use groups?" sections with link to concepts page (#379)

The CLI and UI group management guides both had identical "Why use groups?"
sections. These are now replaced with a tip admonition linking to the
comprehensive groups concepts page, which covers when and why to use groups
in detail.

Addresses follow-up from PR #363.

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

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

Author: jhrozek

docs/toolhive/guides-cli/group-management.mdx

@@ -5,17 +5,15 @@ description:
 ---
 
 This guide explains how to organize your MCP servers into logical groups and
-configure which groups your MCP clients can access. Groups help you organize
-servers by project, environment, or team, and control which tools are available
-to different clients.
+configure which groups your MCP clients can access.
 
-## Why use groups?
+:::tip[New to groups?]
 
-Groups let you organize MCP servers and control client access:
+If you're not sure whether groups are right for your use case, see
+[Organizing MCP servers with groups](../concepts/groups.mdx) for an overview of
+when and why to use them.
 
-- **Project isolation**: Keep development and production servers separate
-- **Environment management**: Organize servers by development stage
-- **Client customization**: Configure different tool sets for different clients
+:::
 
 :::info[What's the default behavior?]
 

docs/toolhive/guides-ui/group-management.mdx

@@ -6,17 +6,15 @@ description:
 ---
 
 This guide explains how to organize your MCP servers into groups and configure
-which groups your MCP clients can access. Groups help you organize servers by
-project, environment, or team, and control which tools are available to
-different clients.
+which groups your MCP clients can access.
 
-## Why use groups?
+:::tip[New to groups?]
 
-Groups let you organize MCP servers and control client access:
+If you're not sure whether groups are right for your use case, see
+[Organizing MCP servers with groups](../concepts/groups.mdx) for an overview of
+when and why to use them.
 
-- **Project isolation**: Keep development and production servers separate
-- **Environment management**: Organize servers by development stage
-- **Client customization**: Configure different tool sets for different clients
+:::
 
 :::info[What's the default behavior?]