feat: Implement delayed Ctrl+C exit prompt

This change introduces a small delay after the first Ctrl+C press, prompting the user to press Ctrl+C again to exit. This helps prevent accidental termination of the application.

- Added `exitOnCtrlC={false}` to the Ink render options in `gemini.tsx` to enable custom Ctrl+C handling.
- Implemented logic in `App.tsx` to:
    - Display "Press Ctrl+C again to exit." for 2 seconds after the first Ctrl+C.
    - Exit the application if Ctrl+C is pressed again during this period.
    - Revert to normal operation if the second Ctrl+C is not pressed within the timeout.
- Defined a constant `CTRL_C_PROMPT_DURATION_MS` for the timeout duration.

packages/cli/src/gemini.tsx

@@ -78,6 +78,7 @@ async function main() {
           startupWarnings={startupWarnings}
         />
       </React.StrictMode>,
+      { exitOnCtrlC: false },
     );
     return;
   }

packages/cli/src/ui/App.tsx

@@ -44,6 +44,8 @@ import { useLogger } from './hooks/useLogger.js';
 import { StreamingContext } from './contexts/StreamingContext.js';
 import { useGitBranchName } from './hooks/useGitBranchName.js';
 
+const CTRL_C_PROMPT_DURATION_MS = 1000;
+
 interface AppProps {
   config: Config;
   settings: LoadedSettings;
@@ -77,18 +79,43 @@ export const App = ({
   const [corgiMode, setCorgiMode] = useState(false);
   const [shellModeActive, setShellModeActive] = useState(false);
   const [showErrorDetails, setShowErrorDetails] = useState<boolean>(false);
+  const [ctrlCPressedOnce, setCtrlCPressedOnce] = useState(false);
+  const ctrlCTimerRef = useRef<NodeJS.Timeout | null>(null);
 
   const errorCount = useMemo(
     () => consoleMessages.filter((msg) => msg.type === 'error').length,
     [consoleMessages],
   );
+
   useInput((input: string, key: InkKeyType) => {
     if (key.ctrl && input === 'o') {
       setShowErrorDetails((prev) => !prev);
       refreshStatic();
+    } else if (key.ctrl && (input === 'c' || input === 'C')) {
+      if (ctrlCPressedOnce) {
+        if (ctrlCTimerRef.current) {
+          clearTimeout(ctrlCTimerRef.current);
+        }
+        process.exit(0);
+      } else {
+        setCtrlCPressedOnce(true);
+        ctrlCTimerRef.current = setTimeout(() => {
+          setCtrlCPressedOnce(false);
+          ctrlCTimerRef.current = null;
+        }, CTRL_C_PROMPT_DURATION_MS);
+      }
     }
   });
 
+  useEffect(
+    () => () => {
+      if (ctrlCTimerRef.current) {
+        clearTimeout(ctrlCTimerRef.current);
+      }
+    },
+    [],
+  );
+
   useConsolePatcher({
     onNewMessage: handleNewMessage,
     debugMode: config.getDebugMode(),
@@ -365,11 +392,17 @@ export const App = ({
                   {process.env.GEMINI_SYSTEM_MD && (
                     <Text color={Colors.AccentRed}>|⌐■_■| </Text>
                   )}
-                  {geminiMdFileCount > 0 && (
+                  {ctrlCPressedOnce ? (
+                    <Text color={Colors.AccentYellow}>
+                      Press Ctrl+C again to exit.
+                    </Text>
+                  ) : geminiMdFileCount > 0 ? (
                     <Text color={Colors.SubtleComment}>
                       Using {geminiMdFileCount} GEMINI.md file
                       {geminiMdFileCount > 1 ? 's' : ''}
                     </Text>
+                  ) : (
+                    <Text> </Text> // Render an empty space to reserve height
                   )}
                 </Box>
                 <Box>