fix(setup): register step uses engage_mode columns dropped by migration 010

Migration 010-engage-modes (replace trigger_rules + response_scope with
engage_mode/engage_pattern/sender_scope/ignored_message_policy) updated
the schema and the production code paths, but missed setup/register.ts.

The step still constructed a payload with the dropped columns. On any
fresh v2 install, attempting to register a channel via:

  pnpm exec tsx setup/index.ts --step register -- --platform-id ...

fails with: `Missing named parameter "engage_mode"`. This affects every
flow that calls the register step — the /add-<channel> skills,
/manage-channels, and the setup auto driver.

Map old → new:
- trigger_rules.pattern (string) → engage_mode='pattern',
  engage_pattern=<pattern>
- requiresTrigger=false (no pattern) → engage_mode='pattern',
  engage_pattern='.' (the "always" sentinel from migration 010)
- requiresTrigger=true (no pattern) → engage_mode='mention'
- response_scope='all' → sender_scope='all',
  ignored_message_policy='drop' (conservative default matching the
  migration backfill rule)

Tested by registering three Telegram channels (one DM, two groups) on a
fresh v2 install — all succeeded.

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

setup/register.ts

@@ -167,18 +167,16 @@ export async function run(args: string[]): Promise<void> {
   if (!existing) {
     newlyWired = true;
     const mgaId = generateId('mga');
-    const triggerRules = parsed.trigger
-      ? JSON.stringify({
-          pattern: parsed.trigger,
-          requiresTrigger: parsed.requiresTrigger,
-        })
-      : null;
+    const engageMode = parsed.trigger || !parsed.requiresTrigger ? 'pattern' : 'mention';
+    const engagePattern = parsed.trigger ? parsed.trigger : (!parsed.requiresTrigger ? '.' : null);
     createMessagingGroupAgent({
       id: mgaId,
       messaging_group_id: messagingGroup.id,
       agent_group_id: agentGroup.id,
-      trigger_rules: triggerRules,
-      response_scope: 'all',
+      engage_mode: engageMode,
+      engage_pattern: engagePattern,
+      sender_scope: 'all',
+      ignored_message_policy: 'drop',
       session_mode: parsed.sessionMode,
       priority: 0,
       created_at: new Date().toISOString(),