fix(register): wire channels with correct engage fields, skip prefix for native IDs

setup/register.ts had two bugs that prevented new channels from being
registered via `/manage-channels`:

1. createMessagingGroupAgent was called with the legacy field names
   `trigger_rules` and `response_scope`. The SQL INSERT expects
   `engage_mode` / `engage_pattern` / `sender_scope` / `ignored_message_policy`
   (migration 010). Every register call failed with
   `RangeError: Missing named parameter "engage_mode"` after the agent
   and messaging group were partially created — leaving an orphaned pair.

   Now mirrors scripts/init-first-agent.ts:wireIfMissing:
   - Groups (is_group=1) default to engage_mode='mention' (bot only
     responds when addressed).
   - DMs (is_group=0) default to engage_mode='pattern' with '.' (respond
     to every message).
   - An explicit --trigger overrides the pattern regex.

2. The "normalize platform_id" block unconditionally prefixed
   "<channel>:" even for native IDs like WhatsApp JIDs
   ("120363408974444974@g.us"), iMessage emails ("user@example.com"),
   or Signal phones ("+15551234567") / Signal groups ("group:abc"). But
   the router (src/router.ts:158) looks up messaging_groups by the raw
   event.platformId from the adapter, which for these native adapters
   never has a prefix. So the prefixed row was never matched — the
   message was silently dropped with no "Message routed" log.

   Extracted scripts/init-first-agent.ts:namespacedPlatformId into
   src/platform-id.ts so both setup paths use the same heuristic (skip
   the prefix for IDs containing '@', starting with '+', or starting
   with 'group:'). Prevents future drift between the two paths.

Tested by: re-running `setup/index.ts --step register` for a WhatsApp
group JID, confirming the row is created with correct engage fields
and matching platform_id, then sending a test message and observing
"Message routed" with the right agent group.

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

setup/register.ts

@@ -20,6 +20,7 @@ import {
 import { isValidGroupFolder } from '../src/group-folder.js';
 import { initGroupFilesystem } from '../src/group-init.js';
 import { log } from '../src/log.js';
+import { namespacedPlatformId } from '../src/platform-id.js';
 import { resolveSession, writeSessionMessage } from '../src/session-manager.js';
 import { emitStatus } from './status.js';
 
@@ -112,12 +113,10 @@ export async function run(args: string[]): Promise<void> {
     process.exit(4);
   }
 
-  // Chat SDK adapters prefix platform IDs with the channel type
-  // (e.g. "telegram:123", "discord:guild:channel"). Normalize here so
-  // the stored ID always matches what the adapter sends at runtime.
-  if (!parsed.platformId.startsWith(`${parsed.channel}:`)) {
-    parsed.platformId = `${parsed.channel}:${parsed.platformId}`;
-  }
+  // Normalize platform_id to the same shape the adapter will emit at runtime,
+  // so the router's (channel_type, platform_id) lookup matches what we store.
+  // Chat SDK adapters prefix, native adapters (WhatsApp/iMessage/Signal) don't.
+  parsed.platformId = namespacedPlatformId(parsed.channel, parsed.platformId);
 
   log.info('Registering channel', parsed);
 
@@ -167,8 +166,13 @@ export async function run(args: string[]): Promise<void> {
   if (!existing) {
     newlyWired = true;
     const mgaId = generateId('mga');
-    const engageMode = parsed.trigger || !parsed.requiresTrigger ? 'pattern' : 'mention';
-    const engagePattern = parsed.trigger ? parsed.trigger : (!parsed.requiresTrigger ? '.' : null);
+    // Mirrors scripts/init-first-agent.ts:wireIfMissing so both setup paths
+    // create rows with the same shape. Groups default to 'mention' (bot only
+    // responds when addressed); DMs default to 'pattern'/'.' (respond to
+    // every message). An explicit --trigger overrides the pattern regex.
+    const isGroup = messagingGroup.is_group === 1;
+    const engageMode: 'pattern' | 'mention' = isGroup && !parsed.trigger ? 'mention' : 'pattern';
+    const engagePattern: string | null = engageMode === 'pattern' ? parsed.trigger || '.' : null;
     createMessagingGroupAgent({
       id: mgaId,
       messaging_group_id: messagingGroup.id,
@@ -177,7 +181,7 @@ export async function run(args: string[]): Promise<void> {
       engage_pattern: engagePattern,
       sender_scope: 'all',
       ignored_message_policy: 'drop',
-      session_mode: parsed.sessionMode,
+      session_mode: parsed.sessionMode as 'shared' | 'per-thread' | 'agent-shared',
       priority: 0,
       created_at: new Date().toISOString(),
     });