feat: initial implementation of Focus RSVP speed reader

- Pure frontend SPA (Vite + React 19 + TypeScript + Tailwind CSS v4)
- Spritz ORP engine with absolute center crosshair gaze fixation
- Multilingual hybrid segmentation via Intl.Segmenter with punctuation attachment
- Adaptive breathing rhythm delay algorithm for natural comprehension
- IndexedDB local bookshelf, progress persistence, and client-side EPUB/TXT/MD parsing
- Curated sci-fi, philosophy, and classic speech samples
- Dark/OLED/Sepia/Slate/Nord themes and rich keyboard controls

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

index.html

@@ -0,0 +1,15 @@
+<!doctype html>
+<html lang="zh-CN">
+  <head>
+    <meta charset="UTF-8" />
+    <link rel="icon" type="image/svg+xml" href="/favicon.svg" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
+    <meta name="theme-color" content="#09090b" />
+    <meta name="description" content="Focus — 极致极速 RSVP 闪屏阅读器，基于 Spritz ORP 中心锚定与自适应呼吸节奏算法，眼球完全静止，秒进专注流。" />
+    <title>Focus — 极速 RSVP 闪屏专注阅读器</title>
+  </head>
+  <body class="bg-black select-none">
+    <div id="root"></div>
+    <script type="module" src="/src/main.tsx"></script>
+  </body>
+</html>