chore: Use primary agent's model as fallback for subagents (#304)

src/cli/helpers/subagentAggregation.ts

@@ -108,6 +108,7 @@ export function createSubagentGroupItem(
         totalTokens: subagent.totalTokens,
         agentURL: subagent.agentURL,
         error: subagent.error,
+        model: subagent.model,
       });
     }
   }

src/cli/helpers/subagentState.ts

@@ -26,6 +26,7 @@ export interface SubagentState {
   totalTokens: number;
   durationMs: number;
   error?: string;
+  model?: string;
   startTime: number;
   toolCallId?: string; // Links this subagent to its parent Task tool call
 }