feat(policy): map --yolo to allowedTools wildcard policy

This PR maps the `--yolo` flag natively into a wildcard policy array
(`allowedTools: ["*"]`) and removes the concept of `ApprovalMode.YOLO` as a
distinct state in the application, fulfilling issue #11303.

This removes the hardcoded `ApprovalMode.YOLO` state and its associated
UI/bypasses. The `PolicyEngine` now evaluates YOLO purely via data-driven rules.

- Removes `ApprovalMode.YOLO`
- Removes UI toggle (`Ctrl+Y`) and indicators for YOLO
- Removes `yolo.toml`
- Updates A2A server and CLI config logic to translate YOLO into a wildcard tool
- Rewrites policy engine tests to evaluate the wildcard
- Enforces enterprise `disableYoloMode` and `secureModeEnabled` controls
  by actively preventing manual `--allowed-tools=*` bypasses.

Fixes #11303

packages/a2a-server/src/agent/task-event-driven.test.ts

@@ -9,7 +9,6 @@ import {
   type Config,
   MessageBusType,
   ToolConfirmationOutcome,
-  ApprovalMode,
   Scheduler,
   type MessageBus,
 } from '@google/gemini-cli-core';
@@ -358,7 +357,7 @@ describe('Task Event-Driven Scheduler', () => {
     // Enable YOLO mode
     const yoloConfig = createMockConfig({
       isEventDrivenSchedulerEnabled: () => true,
-      getApprovalMode: () => ApprovalMode.YOLO,
+      getAllowedTools: () => ['*'],
     }) as Config;
     const yoloMessageBus = yoloConfig.messageBus;