fix: finalize durable Pi lifecycle

backend/src/settings/settings-cli.ts

@@ -1,7 +1,15 @@
 /* Core-side, non-interactive installation-default writer used only through compose exec.
  * It accepts no credentials and writes the same SETTINGS_FILE consumed by session creation. */
+import { readFileSync } from "node:fs";
 import { loadConfig } from "../config.js";
-import { loadSettings, saveSettings, type Settings } from "./settings-store.js";
+import {
+  captureSettingsSnapshot,
+  loadSettings,
+  restoreSettingsSnapshot,
+  saveSettings,
+  type Settings,
+  type SettingsSnapshot,
+} from "./settings-store.js";
 
 const choice = /^[A-Za-z0-9][A-Za-z0-9._/-]{0,127}$/;
 
@@ -15,15 +23,25 @@ function value(args: string[], flag: string): string {
 
 try {
   const args = process.argv.slice(2);
-  if (args.length !== 6) throw new Error("only provider, model, and thinking may be configured");
-  const provider = value(args, "--provider");
-  const model = value(args, "--model");
-  const thinking = value(args, "--thinking");
-  if (!choice.test(provider) || !choice.test(model)) throw new Error("invalid provider or model");
-  if (!["low", "medium", "high"].includes(thinking)) throw new Error("invalid thinking level");
   const cfg = loadConfig(process.env);
-  const next: Settings = { ...loadSettings(cfg), provider, model, thinking };
-  saveSettings(cfg, next);
+  if (args.length === 1 && args[0] === "--snapshot") {
+    process.stdout.write(`${JSON.stringify(captureSettingsSnapshot(cfg))}\n`);
+  } else if (args.length === 1 && args[0] === "--restore") {
+    const parsed = JSON.parse(readFileSync(0, "utf8")) as Partial<SettingsSnapshot>;
+    if (Object.keys(parsed).some((key) => key !== "exists" && key !== "rawBase64")) {
+      throw new Error("invalid settings snapshot");
+    }
+    restoreSettingsSnapshot(cfg, parsed as SettingsSnapshot);
+  } else {
+    if (args.length !== 6) throw new Error("only provider, model, and thinking may be configured");
+    const provider = value(args, "--provider");
+    const model = value(args, "--model");
+    const thinking = value(args, "--thinking");
+    if (!choice.test(provider) || !choice.test(model)) throw new Error("invalid provider or model");
+    if (!["low", "medium", "high"].includes(thinking)) throw new Error("invalid thinking level");
+    const next: Settings = { ...loadSettings(cfg), provider, model, thinking };
+    saveSettings(cfg, next);
+  }
 } catch (error) {
   process.stderr.write(`settings-cli: ${error instanceof Error ? error.message : "invalid configuration"}\n`);
   process.exitCode = 2;