docs(readme): add "Jump to a topic" quick-nav right under the previews

First-fold visitors can now jump to a specific category without scrolling
to the full Tutorial Index. 8 categories listed as inline dot-separated
links: General · Post-Training · Architecture · Generative · Generation
Systems · Multimodal · Agents · Embodied AI (community). Plus a single
fallback link to the full Tutorial Index for completeness.

Placed right after the homepage preview block, before "📱 HTML reads
cleanly everywhere" — same first-fold position as the existing 🔥 NEW
callout. Bilingual parity maintained.

Author: wanshuiyin

README.md

@@ -30,6 +30,14 @@ Each cheat sheet is a long-form Chinese tutorial with: formula derivations · fr
 
 > 🌐 **ARIS-Homepage preview** (above): same `/render-html` workflow turning a CV into a fact-checked academic homepage. Live demo at [wanshuiyin.github.io](https://wanshuiyin.github.io/). Details + pipeline diagram in the [ARIS-Homepage section ↓](#-aris-homepage--fact-checked-academic-homepage-from-cv).
 
+### 📚 Jump to a topic
+
+23 first-party cheat sheets across 7 categories + 1 community-contributed category — pick a domain:
+
+[🧠 General / Foundations](#-general--foundations) · [🎯 Post-Training & Reasoning](#-post-training--reasoning) · [🏛️ LLM Architecture & Systems](#-llm-architecture--systems) · [🌊 Generative Models — Theory & Tokenizers](#-generative-models--theory--tokenizers) · [🎨 Generation Systems (Image / Video / 3D / Diffusion Post-Training)](#-generation-systems--image--video--3d--diffusion-post-training) · [👁️ Multimodal](#-multimodal) · [🤖 Agents](#-agents) · [🦾 Embodied AI / 具身智能](#-embodied-ai--具身智能)
+
+Or browse the full [📚 Tutorial Index ↓](#-tutorial-index).
+
 ### 📱 HTML reads cleanly everywhere
 
 Phone on the subway, iPad at a café, laptop in the library — same HTML link opens equally well:

README_CN.md

@@ -30,6 +30,14 @@
 
 > 🌐 **ARIS-Homepage 预览**（上图）：同一套 `/render-html` workflow，把 CV 变成 fact-checked 学术主页。Live demo：[wanshuiyin.github.io](https://wanshuiyin.github.io/)。详情 + 流程图见 [ARIS-Homepage section ↓](#-aris-homepage--fact-checked-学术主页生成器)。
 
+### 📚 按方向直达
+
+23 篇 first-party cheat sheet，7 大方向 + 1 个社区贡献方向，挑你想看的：
+
+[🧠 General / 基础](#-general--基础) · [🎯 Post-Training & Reasoning](#-post-training--reasoning) · [🏛️ LLM Architecture & Systems](#-llm-architecture--systems) · [🌊 Generative Models — 理论 & Tokenizers](#-generative-models--理论--tokenizers) · [🎨 Generation Systems（图像 / 视频 / 3D / Diffusion 后训练）](#-generation-systems--图像--视频--3d--diffusion-后训练) · [👁️ Multimodal](#-multimodal) · [🤖 Agents](#-agents) · [🦾 Embodied AI / 具身智能](#-embodied-ai--具身智能)
+
+或浏览完整 [📚 教程清单 ↓](#-教程清单)。
+
 ### 📱 HTML 格式哪里都能读，清清楚楚
 
 地铁上掏手机、咖啡馆开 iPad、图书馆开笔记本——同一个 HTML 链接打开都能读：