Social SDK: Add Rich Presence without authentication documentation (#7744)

Add comprehensive documentation for using Rich Presence via direct RPC
communication without requiring full Discord authentication. This
enables simpler integration for developers who only need basic presence
functionality while Discord desktop clients are running.

Author: markmandel

docs/discord-social-sdk/development-guides/setting-rich-presence.mdx

@@ -1,7 +1,6 @@
 ---
 sidebar_label: Setting Rich Presence
 ---
-import PublicClient from '../partials/callouts/public-client.mdx';
 import SupportCallout from '../partials/callouts/support.mdx';
 
 [Home](/docs/intro) > [Discord Social SDK](/docs/discord-social-sdk/overview) > [Development Guides](/docs/discord-social-sdk/development-guides) > {sidebar_label}
@@ -198,6 +197,55 @@ activity.SetSupportedPlatforms(discordpp::ActivityGamePlatforms::Desktop);
 
 See the `ActivityGamePlatforms` enum for all supported platforms.
 
+## Rich Presence Without Authentication
+
+:::warn
+Rich Presence via RPC (Remote Procedure Call) will only work with a running Discord desktop client. It does not support mobile, console or web clients.
+:::
+
+Unlike most other features of the Discord Social SDK, **Rich Presence can be set without authentication**. Instead of
+using [`Client::Connect`] to authenticate with Discord, you can use Rich Presence functionality by directly communicating
+with a running Discord desktop client through RPC (Remote Procedure Call).
+
+### Setting Up Direct Rich Presence
+
+To use Rich Presence without authentication, simply:
+
+1. Set your application ID using [`Client::SetApplicationId`]
+2. Configure your activity details
+3. Call [`Client::UpdateRichPresence`]
+
+```cpp
+auto client = std::make_shared<discordpp::Client>();
+
+// Set the application ID (no Connect() call needed)
+client->SetApplicationId(APPLICATION_ID);
+
+// Configure rich presence details
+discordpp::Activity activity;
+activity.SetType(discordpp::ActivityTypes::Playing);
+activity.SetState("In Competitive Match");
+activity.SetDetails("Rank: Diamond II");
+
+// Update rich presence
+client->UpdateRichPresence(
+    activity, [](const discordpp::ClientResult &result) {
+      if (result.Successful()) {
+        std::cout << "🎮 Rich Presence updated successfully!\n";
+      } else {
+        std::cerr << "❌ Rich Presence update failed";
+      }
+    });
+```
+
+### Requirements
+
+* Discord desktop client must be running on the user's machine
+* Your application must be registered with Discord and have a valid Application ID
+
+This direct approach makes Rich Presence integration much simpler for developers who only need basic presence
+functionality while Discord desktop clients are running.
+
 ---
 
 ## Next Steps
@@ -228,4 +276,7 @@ Now that you've set up Rich Presence, you might want to explore:
 
 {/* Autogenerated Reference Links */}
 [`Activity`]: https://discord.com/developers/docs/social-sdk/classdiscordpp_1_1Activity.html#ae793d9adbe16fef402b859ba02bee682
-[`ActivityTypes`]: https://discord.com/developers/docs/social-sdk/namespacediscordpp.html#a6c76a8cbbc9270f025fd6854d5558660
+[`ActivityTypes`]: https://discord.com/developers/docs/social-sdk/namespacediscordpp.html#a6c76a8cbbc9270f025fd6854d5558660
+[`Client::Connect`]: https://discord.com/developers/docs/social-sdk/classdiscordpp_1_1Client.html#a873a844c7c4c72e9e693419bb3e290aa
+[`Client::SetApplicationId`]: https://discord.com/developers/docs/social-sdk/classdiscordpp_1_1Client.html#ad452335c06b28be0406dab824acccc49
+[`Client::UpdateRichPresence`]: https://discord.com/developers/docs/social-sdk/classdiscordpp_1_1Client.html#af0a85e30f2b3d8a0b502fd23744ee58e