fix(cli): allow @ file selector on slash command lines (#16370)

packages/cli/src/ui/components/InputPrompt.tsx

@@ -18,7 +18,10 @@ import chalk from 'chalk';
 import stringWidth from 'string-width';
 import { useShellHistory } from '../hooks/useShellHistory.js';
 import { useReverseSearchCompletion } from '../hooks/useReverseSearchCompletion.js';
-import { useCommandCompletion } from '../hooks/useCommandCompletion.js';
+import {
+  useCommandCompletion,
+  CompletionMode,
+} from '../hooks/useCommandCompletion.js';
 import type { Key } from '../hooks/useKeypress.js';
 import { useKeypress } from '../hooks/useKeypress.js';
 import { keyMatchers, Command } from '../keyMatchers.js';
@@ -1045,11 +1048,13 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
         scrollOffset={activeCompletion.visibleStartIndex}
         userInput={buffer.text}
         mode={
-          buffer.text.startsWith('/') &&
-          !reverseSearchActive &&
-          !commandSearchActive
-            ? 'slash'
-            : 'reverse'
+          completion.completionMode === CompletionMode.AT
+            ? 'reverse'
+            : buffer.text.startsWith('/') &&
+                !reverseSearchActive &&
+                !commandSearchActive
+              ? 'slash'
+              : 'reverse'
         }
         expandedIndex={expandedSuggestionIndex}
       />