fix(core): resolve scheduler hang and improve policy violation visibility

This PR addresses three core issues with the Policy Engine and Scheduler:
1. Scheduler Hang: Removed a redundant MessageBus listener in Scheduler.ts that caused race conditions in TTY environments.
2. Policy Visibility: Updated ToolGroupMessage.tsx to always display policy violation errors, regardless of verbosity settings.
3. User Feedback: Added emitFeedback to MessageBus.ts to ensure blocked tool calls are reported to the UI.

packages/cli/src/ui/hooks/toolMapping.ts

@@ -10,6 +10,7 @@ import {
   type ToolResultDisplay,
   debugLogger,
   CoreToolCallStatus,
+  type ToolErrorType,
 } from '@google/gemini-cli-core';
 import {
   type HistoryItemToolGroup,
@@ -63,6 +64,7 @@ export function mapToDisplay(
     let progressMessage: string | undefined = undefined;
     let progress: number | undefined = undefined;
     let progressTotal: number | undefined = undefined;
+    let errorType: ToolErrorType | undefined = undefined;
 
     switch (call.status) {
       case CoreToolCallStatus.Success:
@@ -72,6 +74,7 @@ export function mapToDisplay(
       case CoreToolCallStatus.Error:
       case CoreToolCallStatus.Cancelled:
         resultDisplay = call.response.resultDisplay;
+        errorType = call.response.errorType;
         break;
       case CoreToolCallStatus.AwaitingApproval:
         correlationId = call.correlationId;
@@ -114,6 +117,7 @@ export function mapToDisplay(
       progressTotal,
       approvalMode: call.approvalMode,
       originalRequestName: call.request.originalRequestName,
+      errorType,
     };
   });