docs: add warning to distinguish custom field extension vs detail input field extension (#4123)

docs/docs/guides/extending-the-dashboard/custom-form-components/index.md

@@ -5,8 +5,8 @@ title: 'Custom Form Elements'
 The dashboard allows you to create custom form elements that provide complete control over how data is rendered and how users
 interact with forms. This includes:
 
-- **Custom Field Components** - Globally-registered components that can be used to render **custom fields** and **configurable operation arguments**
-- **Detail Form Components** - Form input components that target specific fields of detail pages.
+- **[Custom Field Components](#custom-field-components)** — Globally-registered components that can be used to render **custom fields** and **configurable operation arguments**
+- **[Detail Form Components](#detail-form-components)** — Form input components that target specific fields of detail pages
 
 ## Anatomy of a Form Component
 

docs/docs/guides/extending-the-dashboard/customizing-pages/customizing-detail-pages.md

@@ -7,6 +7,12 @@ customize any existing detail page in the Dashboard.
 
 ## Custom form inputs
 
+:::warning Custom Fields
+This feature replaces inputs for **built-in entity fields** only (like `name`, `description`, `slug`).
+
+To customize the form input for a **custom field** you defined in your plugin, use the [Custom Field Components](/guides/extending-the-dashboard/custom-form-components/#custom-field-components) instead.
+:::
+
 You can replace any of the default form inputs with your own components using the `inputs` property.
 
 Let's say you want to replace the default HTML description editor with a markdown editor component: