docs(ui): name the chart the ui.env example belongs to

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Nicholas Bucher <behappy54321@gmail.com>

Author: Charlesthebird

ui/docs/app-extensions.md

@@ -487,15 +487,22 @@ import { readEnv } from "@/appExtensions";
 const apiUrl = readEnv("EXTENSION_EXAMPLE_API_URL", "https://api.example.test");
 ```
 
-**Set it in a deployment** through the chart's `ui.env`:
+**Set it in a deployment** by getting the variable into the UI container's
+environment. With the `kagent` chart that is `ui.env`, which is passed through to
+the UI deployment verbatim:
 
 ```yaml
+# values.yaml
 ui:
   env:
     - name: EXTENSION_EXAMPLE_API_URL
       value: https://api.example.test
 ```
 
+Any other chart works the same way — the only requirement is that the pod running
+the UI has the variable set. Nothing reads it from Kubernetes directly; the
+container's own startup script reads its environment.
+
 **Set it locally** in `ui/.env`, which is git-ignored — `.env.example` keeps a
 section at the bottom for exactly this, so a branch that installs an extension
 appends rather than editing the application's own settings above it: