refactor: centralize WhatsApp config merging

src/commands/onboard-providers.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, it } from "vitest";
 
 import type { ClawdbotConfig } from "../config/config.js";
 import {
+  mergeWhatsAppConfig,
   setWhatsAppAllowFrom,
   setWhatsAppDmPolicy,
   setWhatsAppSelfChatMode,
@@ -54,4 +55,27 @@ describe("onboard-providers WhatsApp setters", () => {
     expect(next.whatsapp?.selfChatMode).toBe(true);
     expect(next.whatsapp?.allowFrom).toEqual(["+15555550123"]);
   });
+
+  it("merges WhatsApp config without clobbering fields", () => {
+    const cfg: ClawdbotConfig = {
+      whatsapp: {
+        dmPolicy: "pairing",
+        allowFrom: ["*"],
+      },
+    };
+
+    const merged = mergeWhatsAppConfig(cfg, {
+      dmPolicy: "open",
+      allowFrom: undefined,
+    });
+    const cleared = mergeWhatsAppConfig(
+      cfg,
+      { allowFrom: undefined },
+      { unsetOnUndefined: ["allowFrom"] },
+    );
+
+    expect(merged.whatsapp?.dmPolicy).toBe("open");
+    expect(merged.whatsapp?.allowFrom).toEqual(["*"]);
+    expect(cleared.whatsapp?.allowFrom).toBeUndefined();
+  });
 });

src/commands/onboard-providers.ts

@@ -1,7 +1,8 @@
 import fs from "node:fs/promises";
 import path from "node:path";
 import type { ClawdbotConfig } from "../config/config.js";
-import type { DmPolicy, WhatsAppConfig } from "../config/types.js";
+import { mergeWhatsAppConfig } from "../config/merge-config.js";
+import type { DmPolicy } from "../config/types.js";
 import {
   listDiscordAccountIds,
   resolveDefaultDiscordAccountId,
@@ -249,20 +250,7 @@ async function noteSlackTokenHelp(
   );
 }
 
-export function mergeWhatsAppConfig(
-  cfg: ClawdbotConfig,
-  patch: Partial<WhatsAppConfig>,
-): ClawdbotConfig {
-  const base = cfg.whatsapp ?? {};
-  return {
-    ...cfg,
-    whatsapp: {
-      selfChatMode: base.selfChatMode,
-      ...base,
-      ...patch,
-    },
-  };
-}
+export { mergeWhatsAppConfig };
 
 export function setWhatsAppDmPolicy(
   cfg: ClawdbotConfig,
@@ -275,7 +263,11 @@ export function setWhatsAppAllowFrom(
   cfg: ClawdbotConfig,
   allowFrom?: string[],
 ): ClawdbotConfig {
-  return mergeWhatsAppConfig(cfg, { allowFrom });
+  return mergeWhatsAppConfig(
+    cfg,
+    { allowFrom },
+    { unsetOnUndefined: ["allowFrom"] },
+  );
 }
 
 function setMessagesResponsePrefix(