feat(core): the e-mail server after Java, measured against Java

SMTP on port 25 stores mails for the domain's accounts as Java reads
them anew and tells a local sender of unknown recipients; POP3 on port
110 hands them out. The mailboxes are in the snapshot and go back into
the project. EmailRun plays four stories over the network; MailCases
feeds Java's workers without one (26 cases, de and en). 18 cases name
Java bugs that the core does not take.

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

packages/core/src/runtime/snapshot.ts

@@ -21,6 +21,7 @@ import type {
   SimpleClientConfiguration,
   SwitchConfiguration,
   WebServerConfiguration,
+  EmailServerAccount,
 } from './config.js';
 import type { VirtualFileSystem } from '../model/virtualFileSystem.js';
 import type { PageLanguage } from './apps/routerPages.js';
@@ -30,6 +31,17 @@ export interface WebServerSnapshot extends WebServerConfiguration {
   readonly isActive: boolean;
 }
 
+/**
+ * An installed e-mail server (EmailServer): its domain, its accounts with
+ * their mailboxes, and whether it is switched on. Java's server keeps its
+ * accounts in /mailserver/konten.txt; the model's are what Java loads from it.
+ */
+export interface EmailServerSnapshot {
+  readonly domain: string;
+  readonly accounts: readonly EmailServerAccount[];
+  readonly isActive: boolean;
+}
+
 /** An installed echo server: its port, and whether it is switched on (Java: ServerBaustein.aktiv). */
 export interface EchoServerSnapshot extends EchoServerConfiguration {
   readonly isActive: boolean;
@@ -88,6 +100,8 @@ export interface TopologySnapshot {
   readonly webServersByNodeId: ReadonlyMap<Id, WebServerSnapshot>;
   /** The nodes with the web browser installed (WebBrowser). */
   readonly webBrowserNodeIds: ReadonlySet<Id>;
+  /** The installed e-mail servers, by node; a run's deliveries change their mailboxes here. */
+  readonly emailServersByNodeId: ReadonlyMap<Id, EmailServerSnapshot>;
   /** Each node's files, which its programs read (a web server its pages). */
   readonly fileSystemsByNodeId: ReadonlyMap<Id, VirtualFileSystem>;
   /** The language of the pages the devices write themselves (a router's), as Java's in the locale it runs in. */
@@ -112,6 +126,7 @@ export interface TopologySnapshotInput {
   simpleClientsByNodeId?: ReadonlyMap<Id, SimpleClientConfiguration>;
   webServersByNodeId?: ReadonlyMap<Id, WebServerSnapshot>;
   webBrowserNodeIds?: ReadonlySet<Id>;
+  emailServersByNodeId?: ReadonlyMap<Id, EmailServerSnapshot>;
   fileSystemsByNodeId?: ReadonlyMap<Id, VirtualFileSystem>;
   language?: PageLanguage;
 }
@@ -135,6 +150,7 @@ export function topologySnapshot(input: TopologySnapshotInput): TopologySnapshot
     simpleClientsByNodeId: input.simpleClientsByNodeId ?? new Map(),
     webServersByNodeId: input.webServersByNodeId ?? new Map(),
     webBrowserNodeIds: input.webBrowserNodeIds ?? new Set(),
+    emailServersByNodeId: input.emailServersByNodeId ?? new Map(),
     fileSystemsByNodeId: input.fileSystemsByNodeId ?? new Map(),
     language: input.language ?? 'de',
   };