feat(DockerHost): Add DockerHost.ping() to check Docker daemon availability and document health-check usage

ts/classes.host.ts

@@ -74,6 +74,18 @@ export class DockerHost {
     await this.imageStore.stop();
   }
 
+  /**
+   * Ping the Docker daemon to check if it's running and accessible
+   * @returns Promise that resolves if Docker is available, rejects otherwise
+   * @throws Error if Docker ping fails
+   */
+  public async ping(): Promise<void> {
+    const response = await this.request('GET', '/_ping');
+    if (response.statusCode !== 200) {
+      throw new Error(`Docker ping failed with status ${response.statusCode}`);
+    }
+  }
+
   /**
    * authenticate against a registry
    * @param userArg