docs: typeahead prop doc (#17812)

packages/react/src/components/ComboBox/ComboBox.mdx

@@ -69,6 +69,12 @@ changes.
 For more information, checkout the Downshift `useCombobox` props
 [documentation](https://github.com/downshift-js/downshift/tree/v9.0.7/src/hooks/useCombobox#basic-props)
 
+## typeahead Prop
+
+The `typeahead` prop enables predictive text and autocomplete functionality in the ComboBox. When enabled, it displays inline suggestions as you type, using a built-in prefix-matching filter that ignores the `shouldFilterItem` prop. Pressing `Tab` will complete the input with the first matching suggestion, while arrow keys can still be used to navigate through filtered options.
+
+When combined with the `allowCustomValue` prop, the ComboBox supports both custom values and typeahead suggestions.
+
 ### Combobox `downshiftActions`
 
 The downshift action methods are made available through the `downshiftActions`

packages/react/src/components/ComboBox/ComboBox.stories.js

@@ -141,7 +141,15 @@ export const AutocompleteWithTypeahead = (args) => {
         onChange={args.onChange}
         helperText="Combobox helper text"
         id="carbon-combobox"
-        items={['Apple', 'Orange', 'Banana', 'Pineapple', 'Raspberry', 'Lime']}
+        items={[
+          'Apple',
+          'Apricot',
+          'Avocado',
+          'Banana',
+          'Blackberry',
+          'Blueberry',
+          'Cantaloupe',
+        ]}
         titleText="ComboBox title"
         typeahead
       />