feat(sim): F4.2 the sim protocol, the simulation room and LocalSimHost; M9 measured

packages/protocol holds the one list of /sim messages and checks every
field, naming what is wrong. packages/sim has the simulation room for F and
the web worker: the document's snapshot at start, the engine's clock on the
wall clock with Java's speed as cable delay, subscriptions to cable
activity, a card's new frames and a program's new window lines, capture and
clock kept over a stop, the command line as first action, a core failure
told to every client. LocalSimHost mirrors the document into the worker and
back without echo. M9 in Chromium: 17 examples give the same capture as in
Node, character for character; the room runs in a real worker.

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

playwright.config.ts

@@ -0,0 +1,11 @@
+// The browser tests: what needs a real browser — the core in Chromium (M9),
+// the room in a real web worker, later the editor's gestures (plan §7.2).
+import { defineConfig, devices } from '@playwright/test';
+
+export default defineConfig({
+  testDir: 'packages',
+  testMatch: '**/browser/*.spec.ts',
+  workers: 1,
+  reporter: 'list',
+  projects: [{ name: 'chromium', use: { ...devices['Desktop Chrome'] } }],
+});