fix: BYO agent wizard back navigation (#84)

- Add exitEnabled prop to Screen component
- Disable Screen's exit handler when in BYO sub-steps
- Esc now goes back one step instead of exiting entirely

Author: aidandaly24

src/cli/tui/components/Screen.tsx

@@ -14,6 +14,8 @@ interface ScreenProps {
   /** Optional content to display above the help text at the bottom */
   footerContent?: ReactNode;
   children: ReactNode;
+  /** Whether Escape key triggers onExit (default: true). Set to false when sub-components handle their own back navigation. */
+  exitEnabled?: boolean;
 }
 
 /**
@@ -23,8 +25,17 @@ interface ScreenProps {
  * - Exit handling (Escape / Ctrl+Q)
  * - Help text at the bottom
  */
-export function Screen({ title, color, onExit, helpText, headerContent, footerContent, children }: ScreenProps) {
-  useExitHandler(onExit);
+export function Screen({
+  title,
+  color,
+  onExit,
+  helpText,
+  headerContent,
+  footerContent,
+  children,
+  exitEnabled = true,
+}: ScreenProps) {
+  useExitHandler(onExit, exitEnabled);
 
   const displayHelpText = helpText ?? HELP_TEXT.EXIT;
 

src/cli/tui/screens/agent/AddAgentScreen.tsx

@@ -356,8 +356,16 @@ export function AddAgentScreen({ existingAgentNames, onComplete, onExit }: AddAg
   }
 
   // BYO path
+  // Disable Screen's exit handler when not on first step (sub-components handle back navigation)
+  const byoExitEnabled = byoCurrentIndex === 0;
   return (
-    <Screen title="Add Agent" onExit={onExit} helpText={getHelpText()} headerContent={renderStepIndicator()}>
+    <Screen
+      title="Add Agent"
+      onExit={onExit}
+      helpText={getHelpText()}
+      headerContent={renderStepIndicator()}
+      exitEnabled={byoExitEnabled}
+    >
       <Panel>
         {byoStep === 'codeLocation' && (
           <CodeLocationInput