Docker: add persistent volume install for running containers

For running containers (OpenClaw etc.): install bun + snowball-cli
into persistent /data/ dir, symlink token, import from host.
Survives container restarts without rebuilding image.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: baixianger

README.md

@@ -256,28 +256,31 @@ snowball login --chrome /snap/bin/chromium
 
 In Docker containers or AI agent platforms (OpenClaw, etc.) where there's no browser:
 
+**New image:**
+
 ```dockerfile
-# Option 1: Use official Bun image
 FROM oven/bun:latest
 RUN bun add -g snowball-cli
-
-# Option 2: Add to existing image
-RUN curl -fsSL https://bun.sh/install | bash && \
-    ~/.bun/bin/bun add -g snowball-cli
 ```
 
-Then inject your token at runtime:
+**Running container with persistent volume** (e.g. OpenClaw):
 
 ```bash
-# From host machine
-docker exec <container> snowball import $(snowball export)
-
-# Or via environment variable in docker-compose.yml
-environment:
-  - SNOWBALL_TOKEN=<base64 from snowball export>
+# Install bun + snowball-cli into the persistent directory
+docker exec <container> bash -c "
+  export BUN_INSTALL=/data/.bun
+  curl -fsSL https://bun.sh/install | bash
+  /data/.bun/bin/bun add -g snowball-cli
+  ln -sf /data/.snowball-cli ~/.snowball-cli
+"
+
+# Import token from host
+docker exec <container> /data/.bun/bin/snowball import $(snowball export)
 ```
 
-For OpenClaw AgentSkill config, install the skill:
+Everything lives in `/data/` — survives container restarts.
+
+**Install as OpenClaw AgentSkill:**
 
 ```bash
 bunx skills add https://github.com/baixianger/snowball-cli

README.zh-CN.md

@@ -256,28 +256,31 @@ snowball login --chrome /snap/bin/chromium
 
 在 Docker 容器或 AI Agent 平台（OpenClaw 等）中没有浏览器：
 
+**新镜像：**
+
 ```dockerfile
-# 方式 1：使用官方 Bun 镜像
 FROM oven/bun:latest
 RUN bun add -g snowball-cli
-
-# 方式 2：在已有镜像中安装
-RUN curl -fsSL https://bun.sh/install | bash && \
-    ~/.bun/bin/bun add -g snowball-cli
 ```
 
-运行时注入 token：
+**已运行的容器 + 持久化目录**（如 OpenClaw）：
 
 ```bash
-# 从宿主机注入
-docker exec <容器> snowball import $(snowball export)
-
-# 或通过 docker-compose.yml 环境变量
-environment:
-  - SNOWBALL_TOKEN=<snowball export 输出的 base64>
+# 在持久化目录中安装 bun + snowball-cli
+docker exec <容器> bash -c "
+  export BUN_INSTALL=/data/.bun
+  curl -fsSL https://bun.sh/install | bash
+  /data/.bun/bin/bun add -g snowball-cli
+  ln -sf /data/.snowball-cli ~/.snowball-cli
+"
+
+# 从宿主机导入 token
+docker exec <容器> /data/.bun/bin/snowball import $(snowball export)
 ```
 
-作为 OpenClaw AgentSkill 安装：
+全部装在 `/data/` 下，容器重启不丢。
+
+**作为 OpenClaw AgentSkill 安装：**
 
 ```bash
 bunx skills add https://github.com/baixianger/snowball-cli