feat(app): add composition root

app/AGENTS.md

@@ -0,0 +1,7 @@
+# App Composition Rules
+
+- `app/` is the composition root for runtime wiring.
+- Create registries, stores, command sets, input adapters, and renderer/view adapters here.
+- Do not implement domain rules, command behavior, rendering backend logic, or React UI here.
+- App composition may import from all layers, but lower layers must not import from `app/`.
+- Keep factories testable; avoid module-level mutable singleton state unless explicitly required by the runtime entrypoint.

app/app.ts

@@ -0,0 +1,16 @@
+import { createCommandRegistry } from "@commands/registry";
+import { viewportCommands } from "@commands/viewport";
+import { createInitialAppState } from "@editor/initial-state";
+import { createAppStore } from "@editor/store";
+
+export type ImageStudioApp = ReturnType<typeof createImageStudioApp>;
+
+export function createImageStudioApp(options?: { documentName?: string }) {
+  const registry = createCommandRegistry([...viewportCommands]);
+  const store = createAppStore(createInitialAppState(options?.documentName), registry);
+
+  return {
+    registry,
+    store,
+  };
+}

app/index.ts

@@ -0,0 +1,2 @@
+export type { ImageStudioApp } from "./app";
+export { createImageStudioApp } from "./app";