feat: unify 3 bot services into single process

- Add UNIFIED_MODE flag (default on, disable with UNIFIED_MODE=0)
- Register all 3 Discord bots in one process (claude, codex, review)
- Load all registered groups regardless of agent_type (codex/owner priority)
- Start credential proxy and container cleanup at unified startup
- shouldServiceProcessChat returns true in unified mode
- Add findChannelByName for role-based response routing
- Backward compatible: UNIFIED_MODE=0 restores per-service behavior

src/router.ts

@@ -93,6 +93,13 @@ export function findChannel(
   return channels.find((c) => c.ownsJid(jid));
 }
 
+export function findChannelByName(
+  channels: Channel[],
+  name: string,
+): Channel | undefined {
+  return channels.find((c) => c.name === name);
+}
+
 /**
  * Normalize message text for deduplication comparison.
  * - Trim leading/trailing whitespace