v2 phase 4: channel adapter interface, registry, and host wiring

ChannelAdapter interface with setup/deliver/teardown/setTyping lifecycle.
Self-registration pattern via channel-registry. Host wiring in index-v2
bridges inbound messages to routeInbound and outbound delivery to adapters.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/db/index.ts

@@ -14,6 +14,7 @@ export {
   getMessagingGroup,
   getMessagingGroupByPlatform,
   getAllMessagingGroups,
+  getMessagingGroupsByChannel,
   updateMessagingGroup,
   deleteMessagingGroup,
   createMessagingGroupAgent,

src/db/messaging-groups.ts

@@ -26,6 +26,12 @@ export function getAllMessagingGroups(): MessagingGroup[] {
   return getDb().prepare('SELECT * FROM messaging_groups ORDER BY name').all() as MessagingGroup[];
 }
 
+export function getMessagingGroupsByChannel(channelType: string): MessagingGroup[] {
+  return getDb()
+    .prepare('SELECT * FROM messaging_groups WHERE channel_type = ?')
+    .all(channelType) as MessagingGroup[];
+}
+
 export function updateMessagingGroup(
   id: string,
   updates: Partial<Pick<MessagingGroup, 'name' | 'is_group' | 'admin_user_id'>>,