fix: allow null parentAgentId in agent schemas and projections

packages/app/src/stores/session-store.ts

@@ -106,7 +106,7 @@ export interface Agent {
   requiresAttention?: boolean;
   attentionReason?: "finished" | "error" | "permission" | null;
   attentionTimestamp?: Date | null;
-  parentAgentId?: string;
+  parentAgentId?: string | null;
 }
 
 export interface Command {

packages/app/src/types/agent-directory.ts

@@ -12,5 +12,5 @@ export interface AgentDirectoryEntry {
   requiresAttention?: boolean;
   attentionReason?: "finished" | "error" | "permission" | null;
   attentionTimestamp?: Date | null;
-  parentAgentId?: string;
+  parentAgentId?: string | null;
 }