setup: add ← Back option to Discord, WhatsApp, iMessage channel flows

Picking the wrong messaging channel during setup left users with no way
to bail out — they had to either complete the chosen flow or kill setup
and start over. This adds a Back option to the first prompt of three
channel sub-flows that share the same simple shape (one leading
brightSelect that's easy to extend).

Mechanics:
- New `setup/lib/back-nav.ts` exports a BACK_TO_CHANNEL_SELECTION
  sentinel and ChannelFlowResult type.
- `setup/auto.ts` wraps the channel dispatch in a while-loop; channels
  return BACK_TO_CHANNEL_SELECTION to bounce back to the chooser
  without restarting setup. Channels not yet wired return void and the
  loop exits after one pass, so the change is backwards compatible.
- Discord, WhatsApp, iMessage each add a `← Back to channel selection`
  option to their first prompt.

Telegram, Slack, Teams, and Signal will follow as separate PRs — they
each need a slightly different shape (extra prompt insertions, gating
inside multi-step flows, etc.) and are easier to review independently.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

setup/channels/discord.ts

@@ -27,6 +27,7 @@ import * as p from '@clack/prompts';
 import k from 'kleur';
 
 import * as setupLog from '../logs.js';
+import { BACK_TO_CHANNEL_SELECTION, type ChannelFlowResult } from '../lib/back-nav.js';
 import { brightSelect } from '../lib/bright-select.js';
 import { confirmThenOpen, formatNoteLink } from '../lib/browser.js';
 import { askOperatorRole } from '../lib/role-prompt.js';
@@ -48,8 +49,10 @@ interface AppInfo {
   owner: { id: string; username: string } | null;
 }
 
-export async function runDiscordChannel(displayName: string): Promise<void> {
-  const hasBot = await askHasBotToken();
+export async function runDiscordChannel(displayName: string): Promise<ChannelFlowResult> {
+  const choice = await askHasBotToken();
+  if (choice === 'back') return BACK_TO_CHANNEL_SELECTION;
+  const hasBot = choice === 'yes';
   if (!hasBot) {
     await walkThroughBotCreation();
   }
@@ -142,17 +145,18 @@ export async function runDiscordChannel(displayName: string): Promise<void> {
   }
 }
 
-async function askHasBotToken(): Promise<boolean> {
+async function askHasBotToken(): Promise<'yes' | 'no' | 'back'> {
   const answer = ensureAnswer(
     await brightSelect({
       message: 'Do you already have a Discord bot?',
       options: [
         { value: 'yes', label: 'Yes, I have a bot token ready' },
         { value: 'no', label: "No, walk me through creating one" },
+        { value: 'back', label: '← Back to channel selection' },
       ],
     }),
   );
-  return answer === 'yes';
+  return answer as 'yes' | 'no' | 'back';
 }
 
 async function walkThroughBotCreation(): Promise<void> {

setup/channels/imessage.ts

@@ -33,6 +33,7 @@ import * as p from '@clack/prompts';
 import k from 'kleur';
 
 import * as setupLog from '../logs.js';
+import { BACK_TO_CHANNEL_SELECTION, type ChannelFlowResult } from '../lib/back-nav.js';
 import { brightSelect } from '../lib/bright-select.js';
 import { askOperatorRole } from '../lib/role-prompt.js';
 import { ensureAnswer, fail, runQuietChild } from '../lib/runner.js';
@@ -48,10 +49,11 @@ interface RemoteCreds {
   apiKey: string;
 }
 
-export async function runIMessageChannel(displayName: string): Promise<void> {
+export async function runIMessageChannel(displayName: string): Promise<ChannelFlowResult> {
   const isMac = os.platform() === 'darwin';
 
   const mode = await askMode(isMac);
+  if (mode === 'back') return BACK_TO_CHANNEL_SELECTION;
   let remoteCreds: RemoteCreds | null = null;
 
   if (mode === 'local') {
@@ -139,34 +141,38 @@ export async function runIMessageChannel(displayName: string): Promise<void> {
   }
 }
 
-async function askMode(isMac: boolean): Promise<Mode> {
+async function askMode(isMac: boolean): Promise<Mode | 'back'> {
+  const baseOptions = isMac
+    ? [
+        {
+          value: 'local' as const,
+          label: 'Local (this Mac)',
+          hint: "uses this machine's iMessage account",
+        },
+        {
+          value: 'remote' as const,
+          label: 'Remote (Photon API)',
+          hint: 'the bot lives on another server',
+        },
+      ]
+    : [
+        {
+          value: 'remote' as const,
+          label: 'Remote (Photon API)',
+          hint: 'only option off macOS',
+        },
+      ];
   const choice = ensureAnswer(
-    await brightSelect<Mode>({
+    await brightSelect<Mode | 'back'>({
       message: 'How should iMessage run?',
       initialValue: isMac ? 'local' : 'remote',
-      options: isMac
-        ? [
-            {
-              value: 'local',
-              label: 'Local (this Mac)',
-              hint: "uses this machine's iMessage account",
-            },
-            {
-              value: 'remote',
-              label: 'Remote (Photon API)',
-              hint: 'the bot lives on another server',
-            },
-          ]
-        : [
-            {
-              value: 'remote',
-              label: 'Remote (Photon API)',
-              hint: 'only option off macOS',
-            },
-          ],
+      options: [
+        ...baseOptions,
+        { value: 'back', label: '← Back to channel selection' },
+      ],
     }),
   );
-  setupLog.userInput('imessage_mode', String(choice));
+  if (choice !== 'back') setupLog.userInput('imessage_mode', String(choice));
   return choice;
 }
 

setup/channels/whatsapp.ts

@@ -33,6 +33,7 @@ import * as p from '@clack/prompts';
 import k from 'kleur';
 
 import * as setupLog from '../logs.js';
+import { BACK_TO_CHANNEL_SELECTION, type ChannelFlowResult } from '../lib/back-nav.js';
 import { brightSelect } from '../lib/bright-select.js';
 import { getLaunchdLabel, getSystemdUnit } from '../../src/install-slug.js';
 import {
@@ -53,8 +54,9 @@ const AUTH_CREDS_PATH = path.join(process.cwd(), 'store', 'auth', 'creds.json');
 
 type AuthMethod = 'qr' | 'pairing-code';
 
-export async function runWhatsAppChannel(displayName: string): Promise<void> {
+export async function runWhatsAppChannel(displayName: string): Promise<ChannelFlowResult> {
   const method = await askAuthMethod();
+  if (method === 'back') return BACK_TO_CHANNEL_SELECTION;
   const phone = method === 'pairing-code' ? await askPhoneNumber() : undefined;
 
   const install = await runQuietChild(
@@ -148,7 +150,7 @@ export async function runWhatsAppChannel(displayName: string): Promise<void> {
   }
 }
 
-async function askAuthMethod(): Promise<AuthMethod> {
+async function askAuthMethod(): Promise<AuthMethod | 'back'> {
   const choice = ensureAnswer(
     await brightSelect({
       message: 'How would you like to authenticate with WhatsApp?',
@@ -163,10 +165,14 @@ async function askAuthMethod(): Promise<AuthMethod> {
           label: 'Enter a pairing code on your phone',
           hint: 'no camera needed',
         },
+        {
+          value: 'back',
+          label: '← Back to channel selection',
+        },
       ],
     }),
-  ) as AuthMethod;
-  setupLog.userInput('whatsapp_auth_method', choice);
+  ) as AuthMethod | 'back';
+  if (choice !== 'back') setupLog.userInput('whatsapp_auth_method', choice);
   return choice;
 }