chore: complete @yume → @infiplot rename (post-PR#9)

PR #9 已完成首页和 layout 的视觉品牌迁移，此 commit 补齐剩余的
技术性改名 —— workspace 包名、source import、localStorage 键、
CSS keyframe、内部 header logo、.env.example、README。

- @yume/* → @infiplot/* (6 package.json + 17 imports + lockfile)
- localStorage/sessionStorage: yume:* → infiplot:*
  (含 PR #9 新增的 yume:hintClosed)
- CSS keyframe yume-ripple → infiplot-ripple
- new/play 页面 header logo "云梦" → "InfiPlot"
- 代码注释中的「云梦」style 形容词删除（layout.tsx, page.tsx）
- 根 package.json name + description（描述跟齐 staging
  "AI 实时交互剧情游戏"）
- README: tagline / Vercel deploy URL / 目录树 / engine 描述

保留：prompts.ts 的 LLM 体裁术语「视觉小说/galgame」、CustomForm
placeholder 的「视觉小说画风」（图像模型识别的风格名词）。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -1,17 +1,17 @@
 {
-  "name": "yume",
+  "name": "infiplot",
   "version": "0.1.0",
   "private": true,
-  "description": "AI 驱动的视觉小说（云梦）",
+  "description": "AI 实时交互剧情游戏",
   "license": "UNLICENSED",
   "packageManager": "pnpm@9.12.0",
   "engines": {
     "node": ">=20"
   },
   "scripts": {
-    "dev": "pnpm --filter @yume/web dev",
-    "build": "pnpm --filter @yume/web build",
-    "start": "pnpm --filter @yume/web start",
+    "dev": "pnpm --filter @infiplot/web dev",
+    "build": "pnpm --filter @infiplot/web build",
+    "start": "pnpm --filter @infiplot/web start",
     "lint": "pnpm -r lint",
     "typecheck": "pnpm -r typecheck"
   },