fix(cli): /clear dismisses active /btw side-question dialog (#3431)

The /clear command cleared the history log but left an active /btw
side-question dialog visible in the fixed bottom area, because /btw
stores state in dedicated btwItem state (via setBtwItem) rather than
in history items. The ui.clear callback only called clearItems() and
clearScreen(), never cancelBtw(), so the pending-btw dialog survived.

Call cancelBtw() from ui.clear so /clear (and /reset, /new) abort any
in-flight btw request and null out the btwItem state.

Fixes #3334

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

packages/cli/src/ui/hooks/slashCommandProcessor.test.ts

@@ -14,6 +14,7 @@ import type {
 } from '../commands/types.js';
 import { CommandKind } from '../commands/types.js';
 import type { LoadedSettings } from '../../config/settings.js';
+import type { HistoryItemBtw } from '../types.js';
 import { MessageType } from '../types.js';
 import { BuiltinCommandLoader } from '../../services/BuiltinCommandLoader.js';
 import { FileCommandLoader } from '../../services/FileCommandLoader.js';
@@ -1124,4 +1125,53 @@ describe('useSlashCommandProcessor', () => {
       expect(logSlashCommand).not.toHaveBeenCalled();
     });
   });
+
+  describe('ui.clear and /btw dialog', () => {
+    it('should dismiss an active btw dialog when ui.clear is called', async () => {
+      const result = setupProcessorHook();
+      await waitFor(() => expect(result.current.commandContext).toBeDefined());
+
+      const btwItem: HistoryItemBtw = {
+        type: MessageType.BTW,
+        btw: { question: 'why?', answer: '', isPending: true },
+      };
+
+      act(() => {
+        result.current.commandContext.ui.setBtwItem(btwItem);
+      });
+      await waitFor(() => {
+        expect(result.current.commandContext.ui.btwItem).toEqual(btwItem);
+      });
+
+      act(() => {
+        result.current.commandContext.ui.clear();
+      });
+
+      await waitFor(() => {
+        expect(result.current.commandContext.ui.btwItem).toBeNull();
+      });
+    });
+
+    it('should abort the in-flight btw request when ui.clear is called', async () => {
+      const result = setupProcessorHook();
+      await waitFor(() => expect(result.current.commandContext).toBeDefined());
+
+      const abortController = new AbortController();
+      const abortSpy = vi.spyOn(abortController, 'abort');
+
+      act(() => {
+        result.current.commandContext.ui.btwAbortControllerRef.current =
+          abortController;
+      });
+
+      act(() => {
+        result.current.commandContext.ui.clear();
+      });
+
+      expect(abortSpy).toHaveBeenCalledTimes(1);
+      expect(
+        result.current.commandContext.ui.btwAbortControllerRef.current,
+      ).toBeNull();
+    });
+  });
 });

packages/cli/src/ui/hooks/slashCommandProcessor.ts

@@ -259,6 +259,7 @@ export const useSlashCommandProcessor = (
       ui: {
         addItem,
         clear: () => {
+          cancelBtw();
           clearItems();
           clearScreen();
           refreshStatic();