Prioritize doctor instructions in AI report prompts

- Extract AI prompt construction into a tested utility for report editor generation.

- Make doctor instructions and structured report fields higher priority than old template body and target-region HTML.

- Tell the AI not to carry over default gallbladder or liver descriptions when the doctor asks for another procedure or body part.

- Limit old full-report context length to reduce anchoring on default template content.

- Update README, AGENTS, report editor, design, progress, and testing docs for the AI prompt priority model.

- Add unit tests covering AI prompt priority and old-content truncation.

README.md

@@ -201,6 +201,7 @@ cp .env.example .env.local
 - 本地存储封装和系统设置兼容。
 - 默认报告模板结构和字段配置。
 - 模板 HTML 导出包字段库元数据。
+- AI Prompt 优先级，避免默认模板旧术式覆盖医生新指令。
 - 打印导出入口。
 - 后端权限策略、AI 入参和语音代理帧处理。