fix(doctor): improve sandbox warning when Docker unavailable

src/commands/doctor-sandbox.ts

@@ -188,7 +188,16 @@ export async function maybeRepairSandboxImages(
 
   const dockerAvailable = await isDockerAvailable();
   if (!dockerAvailable) {
-    note("Docker not available; skipping sandbox image checks.", "Sandbox");
+    const lines = [
+      `Sandbox mode is enabled (mode: "${mode}") but Docker is not available.`,
+      "Docker is required for sandbox mode to function.",
+      "Isolated sessions (cron jobs, sub-agents) will fail without Docker.",
+      "",
+      "Options:",
+      "- Install Docker and restart the gateway",
+      "- Disable sandbox mode: openclaw config set agents.defaults.sandbox.mode off",
+    ];
+    note(lines.join("\n"), "Sandbox");
     return cfg;
   }