Merge PR #676: fix Cursor install command in README

The correct Cursor slash command is /add-plugin, not /plugin-add.
Confirmed via the Cursor 2.5 release announcement.

README.md

@@ -28,6 +28,15 @@ Thanks!
 
 **Note:** Installation differs by platform. Claude Code or Cursor have built-in plugin marketplaces. Codex and OpenCode require manual setup.
 
+### Claude Code Official Marketplace
+
+Superpowers is available via the [official Claude plugin marketplace](https://claude.com/plugins/superpowers)
+
+Install the plugin from Claude marketplace:
+
+```bash
+/plugin install superpowers@claude-plugins-official
+```
 
 ### Claude Code (via Plugin Marketplace)
 
@@ -48,9 +57,11 @@ Then install the plugin from this marketplace:
 In Cursor Agent chat, install from marketplace:
 
 ```text
-/plugin-add superpowers
+/add-plugin superpowers
 ```
 
+or search for "superpowers" in the plugin marketplace.
+
 ### Codex
 
 Tell Codex: