refactor(agents): add prometheus agent and normalize agent key lookups

- Add 'prometheus' to BuiltinAgentNameSchema enum
- Update delegate_task parameter names in documentation (agent → subagent_type, background → run_in_background)
- Make agent name comparison case-insensitive in Atlas hook
- Implement case-insensitive agent config lookup in shared utilities
- Relax type signature for disabled agents parameter

🤖 Generated with assistance of OhMyOpenCode

src/hooks/atlas/index.ts

@@ -399,7 +399,7 @@ function isCallerOrchestrator(sessionID?: string): boolean {
    const messageDir = getMessageDir(sessionID)
    if (!messageDir) return false
    const nearest = findNearestMessageWithFields(messageDir)
-   return nearest?.agent === "Atlas"
+   return nearest?.agent?.toLowerCase() === "atlas"
  }
 
 interface SessionState {