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/config.ts

@@ -22,6 +22,9 @@ export const SERVICE_AGENT_TYPE: AgentType =
       ? 'codex'
       : 'claude-code';
 
+/** Unified mode: single process manages all bots. Disable with UNIFIED_MODE=0. */
+export const UNIFIED_MODE = getEnv('UNIFIED_MODE') !== '0';
+
 export function normalizeServiceId(serviceId: string): string {
   if (serviceId === 'codex') {
     return CODEX_MAIN_SERVICE_ID;