[Website] Add Blueprint v2 handlers (noop) (#2657)

## Motivation for the change, related issues

Adds Blueprint v2 handler for the Playground web client and a Blueprint
v2 worker into the Playground remote. Those classes are no-op for now
and will be plugged in in an upcoming PR.

A part of #2586.

## Testing Instructions (or ideally a Blueprint)

CI, but nothing should break since this only adds dead code

Author: adamziel

packages/playground/client/src/blueprints-v2-handler.ts

@@ -0,0 +1,63 @@
+import type { ProgressTracker } from '@php-wasm/progress';
+import type { PlaygroundClient, StartPlaygroundOptions } from '.';
+import { collectPhpLogs, logger } from '@php-wasm/logger';
+import { consumeAPI } from '@php-wasm/universal';
+
+export class BlueprintsV2Handler {
+	constructor(private readonly options: StartPlaygroundOptions) {}
+
+	async bootPlayground(
+		iframe: HTMLIFrameElement,
+		progressTracker: ProgressTracker
+	) {
+		const {
+			blueprint,
+			onClientConnected,
+			corsProxy,
+			mounts,
+			sapiName,
+			scope,
+		} = this.options;
+		const downloadProgress = progressTracker!.stage();
+
+		// Connect the Comlink API client to the remote worker,
+		// boot the playground, and run the blueprint steps.
+		const playground = consumeAPI<PlaygroundClient>(
+			iframe.contentWindow!,
+			iframe.ownerDocument!.defaultView!
+		) as PlaygroundClient;
+		await playground.isConnected();
+		progressTracker.pipe(playground);
+
+		// Connect the Comlink API client to the remote worker download monitor
+		await playground.onDownloadProgress(downloadProgress.loadingListener);
+
+		await playground.boot({
+			mounts,
+			sapiName,
+			scope: scope ?? Math.random().toFixed(16),
+			corsProxyUrl: corsProxy,
+			experimentalBlueprintsV2Runner: true,
+			// Pass the declaration directly – the worker runs the V2 runner.
+			blueprint: blueprint as any,
+		} as any);
+
+		await playground.isReady();
+		downloadProgress.finish();
+
+		collectPhpLogs(logger, playground);
+		onClientConnected?.(playground);
+
+		/**
+		 * Pre-fetch WordPress update checks to speed up the initial wp-admin load.
+		 *
+		 * @see https://github.com/WordPress/wordpress-playground/pull/2295
+		 */
+		// @TODO
+		// if (compiled.features.networking) {
+		// 	await playground.prefetchUpdateChecks();
+		// }
+
+		return playground;
+	}
+}

packages/playground/remote/src/lib/playground-worker-endpoint-blueprints-v2.ts

@@ -0,0 +1,84 @@
+import { EmscriptenDownloadMonitor } from '@php-wasm/progress';
+import { exposeAPI } from '@php-wasm/web';
+import { PlaygroundWorkerEndpoint } from './playground-worker-endpoint';
+import type { WorkerBootOptions } from './playground-worker-endpoint';
+import { runBlueprintV2 } from '@wp-playground/blueprints';
+import type { BlueprintV2Declaration } from '@wp-playground/blueprints';
+/* @ts-ignore */
+import { corsProxyUrl as defaultCorsProxyUrl } from 'virtual:cors-proxy-url';
+
+// post message to parent
+self.postMessage('worker-script-started');
+
+const downloadMonitor = new EmscriptenDownloadMonitor();
+
+class PlaygroundWorkerEndpointV2 extends PlaygroundWorkerEndpoint {
+	override async boot({
+		scope,
+		// mounts = [],
+		wpVersion,
+		phpVersion,
+		sapiName = 'cli',
+		withICU = false,
+		withNetworking = true,
+		corsProxyUrl,
+		blueprint,
+	}: WorkerBootOptions) {
+		if (this.booted) {
+			throw new Error('Playground already booted');
+		}
+		if (corsProxyUrl === undefined) {
+			corsProxyUrl = defaultCorsProxyUrl as any;
+		}
+		this.booted = true;
+		this.scope = scope;
+		this.requestedWordPressVersion = wpVersion;
+
+		try {
+			const knownRemoteAssetPaths = new Set<string>();
+			const siteUrl = this.computeSiteUrl(scope);
+			const requestHandler = await this.createRequestHandler({
+				siteUrl,
+				sapiName,
+				withICU,
+				corsProxyUrl,
+				knownRemoteAssetPaths,
+				withNetworking,
+				phpVersion: phpVersion!,
+			});
+			const primaryPhp = await requestHandler.getPrimaryPhp();
+
+			if (!blueprint) {
+				throw new Error(
+					'Blueprints v2 runner requires a blueprint declaration.'
+				);
+			}
+
+			const streamed = await runBlueprintV2({
+				php: primaryPhp,
+				cliArgs: ['--site-url=' + siteUrl],
+				blueprint: blueprint as BlueprintV2Declaration,
+				onMessage: async (message: any) => {
+					for (const listener of this.blueprintMessageListeners) {
+						await listener(message);
+					}
+				},
+			});
+			await streamed.finished;
+
+			await this.finalizeAfterBoot(
+				requestHandler,
+				withNetworking,
+				knownRemoteAssetPaths
+			);
+			setApiReady();
+		} catch (e) {
+			setAPIError(e as Error);
+			throw e as Error;
+		}
+	}
+}
+
+const [setApiReady, setAPIError] = exposeAPI(
+	new PlaygroundWorkerEndpointV2(downloadMonitor)
+);