docs: fix Codex install — shell marketplace add, then /plugins picker

Codex uses `codex plugin marketplace add` from the shell (not a slash
command) and an interactive `/plugins` picker for installation; the prior
copy used Claude Code's slash commands which don't exist in Codex.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Aditya Thiruvengadam

README.md

@@ -60,14 +60,15 @@ Klarity marketplace with Codex:
 codex plugin marketplace add Klarity-AI/klarity-mcp
 ```
 
-Then, from a **Codex session**, open the plugin picker:
+Then, from a **Codex session**, run:
 
 ```text
 /plugins
 ```
 
-In the picker, switch to the **Klarity** marketplace, open **klarity**, and
-select **Install plugin**.
+Search for **Klarity** and install the plugin.
+
+The first request that hits a Klarity tool will prompt you to sign in.
 
 ## Install — Gemini CLI
 

docs/install/codex.mdx

@@ -23,13 +23,15 @@ Codex splits this into two steps — a shell command to register the marketplace
 codex plugin marketplace add Klarity-AI/klarity-mcp
 ```
 
-**2. From a Codex session**, open the plugin picker:
+**2. From a Codex session**, run:
 
 ```text
 /plugins
 ```
 
-In the picker, switch to the **Klarity** marketplace, open **klarity**, and select **Install plugin**. The first request that hits a Klarity tool will prompt you to sign in.
+Search for **Klarity** and install the plugin.
+
+The first request that hits a Klarity tool will prompt you to sign in.
 
 ## Config file install (API key)