refactor: flatten monorepo to single web package (#12)

Flatten the pnpm monorepo (apps/web + packages/*) into a single web package at the repo root.

- Move app/lib/components/scripts/public to root; drop apps/web and packages/* wrappers
- Rewrite tsconfig paths (@infiplot/*) to ./lib/*; turbopack.root = __dirname
- Update Vercel (no root-directory) and Cloudflare (pnpm build:cf at root) deploy paths
- Regenerate pnpm-lock.yaml to drop stale workspace importers
- Bump engines.node to >=22 to match wrangler

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/engine/index.ts

@@ -0,0 +1,15 @@
+export {
+  startSession,
+  requestScene,
+  visionDecide,
+  requestInsertBeat,
+  requestBeatAudio,
+} from "./orchestrator";
+export { synthesizeBeat } from "./voice";
+export { mergeCharacters } from "./director";
+export type { SceneResult } from "./director";
+export { runArchitect } from "./agents/architect";
+export type { WriterOutput } from "./agents/writer";
+export type { CinematographerOutput } from "./agents/cinematographer";
+export type { InsertBeatPartial } from "@infiplot/types";
+export * from "./prompts";