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>

app/new/page.tsx

@@ -0,0 +1,57 @@
+import Link from "next/link";
+import { CustomForm } from "@/components/CustomForm";
+
+export default function NewPage() {
+  return (
+    <div className="min-h-screen flex flex-col">
+      <header className="px-6 md:px-16 pt-7 md:pt-10 flex items-center justify-between">
+        <Link
+          href="/"
+          className="text-[10px] smallcaps text-clay-700 hover:text-clay-900 transition-colors flex items-center gap-2"
+        >
+          <i className="fa-solid fa-arrow-left text-[9px]" />
+          InfiPlot
+        </Link>
+        <span className="text-[10px] smallcaps text-clay-500">
+          编 织 一 个 世 界
+        </span>
+      </header>
+
+      <section className="px-6 md:px-16 pt-20 md:pt-32 pb-20 md:pb-24 flex-1">
+        <div className="grid grid-cols-12 gap-8 md:gap-16 max-w-6xl">
+          <div className="col-span-12 md:col-span-4 animate-fade-in">
+            <p className="text-[10px] smallcaps text-clay-500 mb-6">
+              Ⅳ · 无 题
+            </p>
+            <h1 className="font-serif text-[44px] md:text-[64px] text-clay-900 leading-[0.96] mb-8">
+              写下
+              <br />
+              <em className="italic text-clay-600">两段</em>
+              <br />
+              文字。
+            </h1>
+            <div className="hairline w-12 mb-6" />
+            <p className="font-serif text-base text-clay-700 leading-[1.7]">
+              第一段，勾勒故事所在的世界。第二段，描述世界应是什么模样 —
+              它的介质、氛围、颗粒感。
+            </p>
+            <p className="font-serif italic text-sm text-clay-500 mt-5 leading-relaxed">
+              两栏皆可任意语言。越具体，回报越具体。
+            </p>
+          </div>
+          <div className="col-span-12 md:col-span-7 md:col-start-6">
+            <CustomForm />
+          </div>
+        </div>
+      </section>
+
+      <footer className="px-6 md:px-16 pb-8">
+        <div className="hairline-full w-full mb-4" />
+        <div className="flex items-center justify-between text-[10px] smallcaps text-clay-500">
+          <span>MMXXVI</span>
+          <span className="num">Ⅰ · Ⅳ</span>
+        </div>
+      </footer>
+    </div>
+  );
+}