docs: improve readability and formatting of README

README.md

@@ -6,26 +6,33 @@ Storyboarding for comics: auto research and frame-by-frame scripts.
 ## 功能概览 / Feature highlights
 - 多步研究：生成查询 → 并行搜索 → 反思补充 → 分镜 JSON。  
   Multi-step research: queries → parallel search → reflection → JSON storyboard.
+
 - 分镜预览：前端逐页渲染，并为每页触发图生成（需模型权限）。  
   Page cards on frontend; each card triggers image gen (requires model access).
+
 - 模型可切换：Gemini 2.5 Flash / Flash Lite / 3 Pro Preview；语言可选（默认中文）。  
   Models: Gemini 2.5 Flash/Flash Lite/3 Pro Preview; language selectable (CN default).
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 - 一键开发启动：`make dev`。  
   One-command dev start: `make dev`.
 
 ## 目录结构 / Project layout
 - `backend/`：LangGraph + FastAPI，含 `/generate_image`。  
   `backend/`: LangGraph + FastAPI with `/generate_image`.
+
 - `frontend/`：Vite + React，展示对话/分镜卡片/图片状态。  
   `frontend/`: Vite + React UI for chat, cards, image status.
+
 - `backend/scripts/test_generate_image.py`：独立图生成测试脚本。  
   `backend/scripts/test_generate_image.py`: standalone image test script.
 
 ## 环境与依赖 / Requirements
 - Python 3.11+（后端）、Node 18+（前端）。  
   Python 3.11+ (backend), Node 18+ (frontend).
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 - 环境变量：`GEMINI_API_KEY`。  
   Env var: `GEMINI_API_KEY`.
+
 - 图生成需 `gemini-3-pro-image-preview` 权限，否则无图/404。  
   Image gen needs access to `gemini-3-pro-image-preview`, else 404/no image.
 
@@ -38,6 +45,7 @@ Storyboarding for comics: auto research and frame-by-frame scripts.
    pip install -e .
    echo "GEMINI_API_KEY=你的密钥" > .env
    ```
+
 2) 前端安装依赖：  
    Install frontend deps:
    ```bash
@@ -55,10 +63,13 @@ Storyboarding for comics: auto research and frame-by-frame scripts.
 ## 常用命令 / Useful commands
 - 后端单独开发：`cd backend && source .venv/bin/activate && langgraph dev`  
   Backend only: `cd backend && source .venv/bin/activate && langgraph dev`
+
 - 前端单独开发：`cd frontend && npm run dev`  
   Frontend only: `cd frontend && npm run dev`
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 - 前端交互生成：页面输入主题 → 分镜逐页渲染 → 每页自动触发图生成（需模型权限）。  
   Frontend flow: enter topic → cards render → each card triggers image gen (model access required).
+
 - 脚本验证图生成：  
   Scripted image test:
   ```bash
@@ -69,7 +80,9 @@ Storyboarding for comics: auto research and frame-by-frame scripts.
 ## 已知注意事项 / Notes
 - 图生成依赖 `gemini-3-pro-image-preview`，未开通会 404/无图；先用脚本验证。  
   Image gen needs `gemini-3-pro-image-preview`; without access expect 404/no image—verify via script.
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 - 分镜 prompt 过长或含链接时可能被过滤，可简化后再触发生成。  
   Long prompts/links may be filtered; simplify and retry if images are missing.
+  
 - 确保 `.env` 被加载（`langgraph dev` 默认读取 `backend/.env`）。  
   Ensure `.env` is loaded (`langgraph dev` reads `backend/.env`).