build: remember last models

src/types.ts

@@ -1,3 +1,10 @@
+/**
+ * Settings stored in ~/.config/opencode-multi-model/settings.json
+ */
+export interface MultiModelSettings {
+  lastModels: string[];
+}
+
 /**
  * Options for launching a multi-model tmux session.
  */
@@ -10,6 +17,8 @@ export interface MultiModelOptions {
   binaryName?: string;
   /** Caller context: 'cli' shows shell commands, 'tool' shows tool instructions. */
   mode: "cli" | "tool";
+  /** Save models to settings file on successful launch (CLI only). */
+  saveToSettings?: boolean;
 }
 
 /**