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.

docs/testing.md

@@ -82,6 +82,7 @@ AI 第三方接口、讯飞语音上游 WebSocket、麦克风权限和真实视
 | 系统设置混淆兼容 | 已覆盖 | `storage.test.ts` |
 | 默认报告模板结构 | 已覆盖 | `defaultContent.test.ts` |
 | 默认字段和 AI Provider | 已覆盖 | `defaultContent.test.ts` |
+| AI Prompt 优先级 | 已覆盖 | `aiPrompt.test.ts`，覆盖医生指令和结构化字段优先于旧模板内容。 |
 | 打印导出入口 | 已覆盖 | `print.test.ts` |
 | 模板列表合并工具 | 已覆盖 | `templateList.test.ts`，防止新增模板被旧本地缓存覆盖。 |
 | 模板导入导出工具 | 已覆盖 | `templateExport.test.ts`，覆盖 HTML 模板包、字段库元数据回导、旧 JSON 导入兼容和文件名清理。 |