feat: F5.3a the simulation rooms on server F

One room per project for everyone in it, held by a few worker_threads,
each room with a replica of the document that Hocuspocus' direct
connection keeps open: changes go in, what the room writes comes back.
/sim?project=... signs in as /sync does and says refusals and partings
as the socket's closing; only a write grant changes the room. The state
names who started the simulation. After the last person the room stays
60 s, then stops, writes back and ends. Freezing stops a running
simulation and refuses to start one, deleting ends the room without
writing back, revoking lets the person go from the room too; a failed
thread ends its rooms, stopping the service stops them all.

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

packages/server/test/harness.ts

@@ -2,9 +2,15 @@
 // test secrets, a project as the service makes it, a person signed in with
 // a ticket as the dashboard signs one, and that person in a project with
 // Hocuspocus' own provider over a real WebSocket (bringing the session's
-// cookie, as the browser does).
+// cookie, as the browser does). The rooms' thread is the real one, bundled
+// by esbuild as the build bundles it.
 
 import { randomUUID } from 'node:crypto';
+import { mkdtempSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join as joinPath } from 'node:path';
+import { pathToFileURL } from 'node:url';
+import { build } from 'esbuild';
 import { HocuspocusProvider, HocuspocusProviderWebsocket } from '@hocuspocus/provider';
 import { expect } from 'vitest';
 import WebSocket from 'ws';
@@ -32,6 +38,18 @@ export function memoryLog(): MemoryLog {
 
 export type TestServer = FiliusServer & { readonly log: MemoryLog; readonly base: string };
 
+let roomThread: Promise<URL> | undefined;
+
+/** src/simWorker.ts bundled into a directory of its own, once a test file. */
+export function bundledRoomThread(): Promise<URL> {
+  roomThread ??= (async () => {
+    const outfile = joinPath(mkdtempSync(joinPath(tmpdir(), 'filius-room-thread-')), 'simWorker.mjs');
+    await build({ entryPoints: [new URL('../src/simWorker.ts', import.meta.url).pathname], bundle: true, platform: 'node', format: 'esm', target: 'node20', outfile, logLevel: 'error' });
+    return pathToFileURL(outfile);
+  })();
+  return roomThread;
+}
+
 export async function startTestServer(store: DocStore, sessions: SessionStore, options: Partial<ServerOptions> = {}): Promise<TestServer> {
   const log = memoryLog();
   const server = await startServer({
@@ -44,6 +62,8 @@ export async function startTestServer(store: DocStore, sessions: SessionStore, o
     serviceKey: SERVICE_KEY,
     origins: [EDITOR_ORIGIN],
     secureCookie: false,
+    workerUrl: await bundledRoomThread(),
+    simThreads: 1,
     ...options,
   });
   return Object.assign(server, { log, base: `http://127.0.0.1:${server.port}` });
@@ -61,14 +81,16 @@ export async function newProject(store: DocStore): Promise<string> {
 export interface Person {
   readonly user?: string;
   readonly login?: string;
+  /** The name the dashboard shows. */
+  readonly name?: string;
   readonly level?: 'read' | 'write';
   /** The cookie the browser brings to /__auth. */
   readonly cookie?: string;
 }
 
 /** The answer of /__auth to a fresh ticket. */
-export function exchange(server: TestServer, project: string, { user = randomUUID(), login = 'ab12', level = 'write', cookie }: Person = {}, next = '/'): Promise<Response> {
-  const ticket = signTicket({ u: user, n: login, d: 'Ada Beispiel', c: '#3366cc', lang: 'de', p: project, lvl: level }, TICKET_SECRET);
+export function exchange(server: TestServer, project: string, { user = randomUUID(), login = 'ab12', name = 'Ada Beispiel', level = 'write', cookie }: Person = {}, next = '/'): Promise<Response> {
+  const ticket = signTicket({ u: user, n: login, d: name, c: '#3366cc', lang: 'de', p: project, lvl: level }, TICKET_SECRET);
   return fetch(`${server.base}/__auth?ticket=${encodeURIComponent(ticket)}&next=${encodeURIComponent(next)}`, {
     redirect: 'manual',
     ...(cookie === undefined ? {} : { headers: { cookie } }),