Replace bootstrap methods with async factories

Controller.bootstrap and Host.bootstrap returned constructor arguments
that the caller had to spread into new Controller/Host, and
DatastoreProvider.bootstrap did the same for datastores. They are
replaced by Controller.fromConfig, Host.fromConfig and
KeyValueDatastore/SubscribableDatastore.fromProvider, which load the
data and return the finished instance.

Closes #1126

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/host/host.ts

@@ -233,13 +233,12 @@ async function startHost() {
 	}
 
 	let hostConnector = new HostConnector(hostConfig, pluginInfos);
-	host = new Host(
+	host = await Host.fromConfig(
 		hostConnector,
 		hostConfig,
 		pluginInfos,
 		Boolean(args.canRestart),
 		Boolean(args.recovery),
-		...await Host.bootstrap(hostConfig)
 	);
 
 	// Handle interrupts

packages/host/src/Host.ts

@@ -329,12 +329,18 @@ export default class Host extends lib.Link {
 		"_warning": "Changes to this file will be overwritten by the controller's copy.",
 	};
 
-	static async bootstrap(hostConfig: lib.HostConfig) {
+	/** Create a host with its mod store loaded from disk */
+	static async fromConfig(
+		connector: HostConnector,
+		hostConfig: lib.HostConfig,
+		pluginInfos: lib.PluginNodeEnvInfo[],
+		canRestart = false,
+		recoveryMode = false,
+	) {
 		const modsDirectory = hostConfig.get("host.mods_directory");
 		await fs.mkdir(modsDirectory, { recursive: true });
-		return [
-			await lib.ModStore.fromDirectory(modsDirectory),
-		] as const;
+		const modStore = await lib.ModStore.fromDirectory(modsDirectory);
+		return new this(connector, hostConfig, pluginInfos, canRestart, recoveryMode, modStore);
 	}
 
 	constructor(