docs: add Hippo memory workflow

AGENTS.md

@@ -172,3 +172,29 @@ Hippo 脚本变化必须额外用隔离 HOME/PATH 和 mock `pi`、`npm`、`hippo
 - `npm run check`：类型、测试和打包检查的完整验证。
 
 若环境缺少依赖或未执行某项验证，交付时明确说明，不以静态检查代替运行结果。
+
+<!-- hippo:start -->
+## Project Memory (Hippo)
+
+At the start of every task, run:
+```bash
+hippo context --auto --budget 1500
+```
+Read the output before writing any code.
+
+On errors or unexpected behaviour:
+```bash
+hippo remember "<description of what went wrong>" --error
+```
+
+On task completion:
+```bash
+hippo outcome --good
+```
+
+When Hippo's Codex wrapper is installed, session-end capture runs automatically.
+If the wrapper is not installed, capture a brief summary manually:
+```bash
+hippo capture --stdin <<< '<decisions, errors, lessons — 2-5 bullets>'
+```
+<!-- hippo:end -->