chore(site): add preset combobox to dynamic parameters page (#19100)

## Description

This PR updates the `CreateWorkspacePageViewExperimental` page to use
the `Combobox` React component for preset selection. This aligns it with
the implementation used in the standard `CreateWorkspacePageView`,
ensuring consistency in UI behavior and component usage across both
pages.

<img width="2084" height="792" alt="Screenshot 2025-07-30 at 13 58 23"
src="https://github.com/user-attachments/assets/b8e4ed37-9c59-499f-b4e3-7aaca847eaa1"
/>

Related to `CreateWorkspacePageView` changes:
https://github.com/coder/coder/pull/19063

site/src/pages/CreateWorkspacePage/CreateWorkspacePageViewExperimental.tsx

@@ -5,16 +5,10 @@ import { ErrorAlert } from "components/Alert/ErrorAlert";
 import { Avatar } from "components/Avatar/Avatar";
 import { Badge } from "components/Badge/Badge";
 import { Button } from "components/Button/Button";
+import { Combobox } from "components/Combobox/Combobox";
 import { Input } from "components/Input/Input";
 import { Label } from "components/Label/Label";
 import { Link } from "components/Link/Link";
-import {
-	Select,
-	SelectContent,
-	SelectItem,
-	SelectTrigger,
-	SelectValue,
-} from "components/Select/Select";
 import { Spinner } from "components/Spinner/Spinner";
 import { Switch } from "components/Switch/Switch";
 import {
@@ -186,30 +180,31 @@ export const CreateWorkspacePageViewExperimental: FC<
 	}, [form.submitCount, form.errors]);
 
 	const [presetOptions, setPresetOptions] = useState([
-		{ label: "None", value: "None" },
+		{ displayName: "None", value: "undefined", icon: "", description: "" },
 	]);
-	useEffect(() => {
-		setPresetOptions([
-			{ label: "None", value: "None" },
-			...presets.map((preset) => ({
-				label: preset.Default ? `${preset.Name} (Default)` : preset.Name,
-				value: preset.ID,
-			})),
-		]);
-	}, [presets]);
-
 	const [selectedPresetIndex, setSelectedPresetIndex] = useState(0);
-
-	// Set default preset when presets are loaded
+	// Build options and keep default label/value in sync
 	useEffect(() => {
-		const defaultPreset = presets.find((preset) => preset.Default);
+		const options = [
+			{ displayName: "None", value: "undefined", icon: "", description: "" },
+			...presets.map((preset) => ({
+				displayName: preset.Default ? `${preset.Name} (Default)` : preset.Name,
+				value: preset.ID,
+				icon: preset.Icon,
+				description: preset.Description,
+			})),
+		];
+		setPresetOptions(options);
+		const defaultPreset = presets.find((p) => p.Default);
 		if (defaultPreset) {
-			// +1 because "None" is at index 0
-			const defaultIndex =
-				presets.findIndex((preset) => preset.ID === defaultPreset.ID) + 1;
-			setSelectedPresetIndex(defaultIndex);
+			const idx = presets.indexOf(defaultPreset) + 1; // +1 for "None"
+			setSelectedPresetIndex(idx);
+			form.setFieldValue("template_version_preset_id", defaultPreset.ID);
+		} else {
+			setSelectedPresetIndex(0); // Explicitly set to "None"
+			form.setFieldValue("template_version_preset_id", undefined);
 		}
-	}, [presets]);
+	}, [presets, form.setFieldValue]);
 
 	const [presetParameterNames, setPresetParameterNames] = useState<string[]>(
 		[],
@@ -572,11 +567,15 @@ export const CreateWorkspacePageViewExperimental: FC<
 									</div>
 									<div className="flex flex-col gap-4">
 										<div className="max-w-lg">
-											<Select
-												value={presetOptions[selectedPresetIndex]?.value}
-												onValueChange={(option) => {
+											<Combobox
+												value={
+													presetOptions[selectedPresetIndex]?.displayName || ""
+												}
+												options={presetOptions}
+												placeholder="Select a preset"
+												onSelect={(value) => {
 													const index = presetOptions.findIndex(
-														(preset) => preset.value === option,
+														(preset) => preset.value === value,
 													);
 													if (index === -1) {
 														return;
@@ -584,21 +583,14 @@ export const CreateWorkspacePageViewExperimental: FC<
 													setSelectedPresetIndex(index);
 													form.setFieldValue(
 														"template_version_preset_id",
-														index === 0 ? undefined : option,
+														// "undefined" string is equivalent to using None option
+														// Combobox requires a value in order to correctly highlight the None option
+														presetOptions[index].value === "undefined"
+															? undefined
+															: presetOptions[index].value,
 													);
 												}}
-											>
-												<SelectTrigger>
-													<SelectValue placeholder={"Select a preset"} />
-												</SelectTrigger>
-												<SelectContent>
-													{presetOptions.map((option) => (
-														<SelectItem key={option.value} value={option.value}>
-															{option.label}
-														</SelectItem>
-													))}
-												</SelectContent>
-											</Select>
+											/>
 										</div>
 										{/* Only show the preset parameter visibility toggle if preset parameters are actually being modified, otherwise it is ineffectual */}
 										{presetParameterNames.length > 0 && (