feat(editor): F4.6a simulation mode and a computer's desktop

Java's mode buttons start and stop the room, now in a worker of the
editor's page (LocalSimHost), with Java's speed slider. While the
simulation runs the design is locked as in Java: no palette, no sheet,
nothing moves, no undo. Cables that carry a frame light up in Java's
green, and a tap on a computer opens its desktop: Java's title, the
software installation first, then the installed programs in the order
of Java's list for the language, a taskbar with the network icon and
the network as the simulation runs it. The room sends that over a new
topic, node:<id>. Desktops stay over a return to the design and show
again at the next start. The programs' windows follow from F4.6b.

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

packages/sim/src/room.ts

@@ -16,7 +16,7 @@
 // keep rising (plan §6.2).
 
 import * as Y from 'yjs';
-import { DEFAULT_SPEED_PERCENT, NetworkRuntimeEngine, captureRows, type CapturedFrame, type CaptureRow, type Id, type LogLine } from '@mdg-filius/core';
+import { DEFAULT_SPEED_PERCENT, NetworkRuntimeEngine, captureRows, interfaceKey, stableGeneratedMacAddress, type CapturedFrame, type CaptureRow, type Id, type LogLine } from '@mdg-filius/core';
 import { docSnapshot } from '@mdg-filius/doc';
 import {
   parseClientMessage,
@@ -25,6 +25,7 @@ import {
   type ClientMessage,
   type ErrorCode,
   type HostMessage,
+  type NodeSettings,
   type SimMode,
   type Topic,
   type TraceFrame,
@@ -47,6 +48,8 @@ interface Client {
   readonly traceSent: Map<Id, number>;
   /** Per program window, how many of its program's lines it has; none while the program does not run (a stop empties it). */
   readonly appSent: Map<string, number>;
+  /** Per computer, the settings last sent (as text). */
+  readonly nodeSent: Map<Id, string>;
 }
 
 /** A program with a window: its lines. */
@@ -79,7 +82,7 @@ export class SimulationRoom {
   /** A new client; it gets the room's state at once. */
   connect(send: (message: HostMessage) => void): number {
     const id = this.nextClient++;
-    this.clients.set(id, { send, topics: new Set(), traceSent: new Map(), appSent: new Map() });
+    this.clients.set(id, { send, topics: new Set(), traceSent: new Map(), appSent: new Map(), nodeSent: new Map() });
     send(this.state());
     return id;
   }
@@ -117,6 +120,7 @@ export class SimulationRoom {
           client.topics.add(topic);
           if (topic.startsWith('trace:')) client.traceSent.delete(topic.slice('trace:'.length));
           if (topic.startsWith('app:')) client.appSent.delete(topic);
+          if (topic.startsWith('node:')) client.nodeSent.delete(topic.slice('node:'.length));
         }
         this.flush([client], true);
         return;
@@ -260,6 +264,14 @@ export class SimulationRoom {
       for (const topic of client.topics) {
         if (topic === 'activity') {
           if (subscribing) client.send(message({ kind: 'activity', links: this.lastActivity }));
+        } else if (topic.startsWith('node:')) {
+          const node = topic.slice('node:'.length);
+          const settings = this.nodeSettings(node);
+          if (settings === undefined) continue;
+          const text = JSON.stringify(settings);
+          if (client.nodeSent.get(node) === text) continue;
+          client.nodeSent.set(node, text);
+          client.send(message({ kind: 'node', node, settings }));
         } else if (topic.startsWith('trace:')) {
           const portId = topic.slice('trace:'.length);
           const reset = !client.traceSent.has(portId);
@@ -288,6 +300,26 @@ export class SimulationRoom {
     }
   }
 
+  /**
+   * A device's first card as the engine runs it (a computer's settings, which
+   * DHCP may change); undefined for a device the simulation never had.
+   */
+  private nodeSettings(id: Id): NodeSettings | undefined {
+    const snapshot = this.engine.state.topologySnapshot;
+    const node = snapshot.nodes.find((each) => each.id === id);
+    if (node === undefined) return undefined;
+    const port = node.ports[0];
+    const device = snapshot.deviceConfigurations.get(id);
+    const card = port === undefined ? undefined : snapshot.interfaceConfigurations.get(interfaceKey(id, port.id));
+    return {
+      ipAddress: device?.ipAddress ?? card?.ipAddress ?? '',
+      subnetMask: device?.subnetMask ?? card?.subnetMask ?? '',
+      defaultGateway: device?.defaultGateway ?? '',
+      dnsServer: device?.dnsServer ?? '',
+      macAddress: port === undefined ? '' : (port.macAddress ?? stableGeneratedMacAddress(port.id)),
+    };
+  }
+
   /** The cables whose cards got frames since the last tick; sent when that changes. */
   private updateActivity(): void {
     const links = new Set<string>();