feat: Add auto-approval for mode switching

Implements automatic approval for mode switching operations when enabled, following
existing auto-approval patterns in the codebase.

Implementation:
- Added `alwaysAllowModeSwitch` to state management
- Updated `isAutoApproved` function in ChatView to handle mode switch requests
- Added mode switch option to AutoApproveMenu with appropriate handler
- Integrated with existing auto-approval flow

Tests:
- Added three test cases in ChatView.auto-approve.test.tsx:
  1. Verifies mode switch auto-approval when enabled
  2. Verifies no auto-approval when mode switch setting is disabled
  3. Verifies no auto-approval when global auto-approval is disabled

The implementation follows existing patterns for other auto-approve features
(read, write, browser, etc.) to maintain consistency in the codebase.

webview-ui/src/components/chat/AutoApproveMenu.tsx

@@ -28,6 +28,8 @@ const AutoApproveMenu = ({ style }: AutoApproveMenuProps) => {
 		setAlwaysAllowBrowser,
 		alwaysAllowMcp,
 		setAlwaysAllowMcp,
+		alwaysAllowModeSwitch,
+		setAlwaysAllowModeSwitch,
 		alwaysApproveResubmit,
 		setAlwaysApproveResubmit,
 		autoApprovalEnabled,
@@ -71,6 +73,13 @@ const AutoApproveMenu = ({ style }: AutoApproveMenuProps) => {
 			enabled: alwaysAllowMcp ?? false,
 			description: "Allows use of configured MCP servers which may modify filesystem or interact with APIs.",
 		},
+		{
+			id: "switchModes",
+			label: "Switch between modes",
+			shortName: "Modes",
+			enabled: alwaysAllowModeSwitch ?? false,
+			description: "Allows automatic switching between different AI modes without requiring approval.",
+		},
 		{
 			id: "retryRequests",
 			label: "Retry failed requests",
@@ -120,6 +129,12 @@ const AutoApproveMenu = ({ style }: AutoApproveMenuProps) => {
 		vscode.postMessage({ type: "alwaysAllowMcp", bool: newValue })
 	}, [alwaysAllowMcp, setAlwaysAllowMcp])
 
+	const handleModeSwitchChange = useCallback(() => {
+		const newValue = !(alwaysAllowModeSwitch ?? false)
+		setAlwaysAllowModeSwitch(newValue)
+		vscode.postMessage({ type: "alwaysAllowModeSwitch", bool: newValue })
+	}, [alwaysAllowModeSwitch, setAlwaysAllowModeSwitch])
+
 	const handleRetryChange = useCallback(() => {
 		const newValue = !(alwaysApproveResubmit ?? false)
 		setAlwaysApproveResubmit(newValue)
@@ -133,6 +148,7 @@ const AutoApproveMenu = ({ style }: AutoApproveMenuProps) => {
 		executeCommands: handleExecuteChange,
 		useBrowser: handleBrowserChange,
 		useMcp: handleMcpChange,
+		switchModes: handleModeSwitchChange,
 		retryRequests: handleRetryChange,
 	}