fix(web): re-add handleChangeConversation to handleNewConversation deps

Supersedes #39865 (closed as superseded; the original branch
drifted against main while the useConversationSelection refactor
landed and the diff was no longer mergeable). Rebuilt on
`upstream/main` (dfac3e524e).

The bug is still present on main:
`useEmbeddedChatbot` calls `handleChangeConversation('')` inside
`handleNewConversation` but only declares it through the closure
instead of in the useCallback dep array. The reset button therefore
captures a stale `handleChangeConversation` identity after any
state change that invalidates its reference (e.g. `userId`).

Adds the missing dep and a regression test that asserts both
handlers regenerate together after an identity-invalidation rerender,
while preserving identity across a no-prop rerender.

web/app/components/base/chat/embedded-chatbot/__tests__/hooks.spec.tsx

@@ -608,6 +608,45 @@ describe('useEmbeddedChatbot', () => {
       expect(result.current.clearChatList).toBe(true)
     })
 
+    // Regression for #38573: handleNewConversation must include handleChangeConversation
+    // in its useCallback deps so the reset button always invokes the freshest
+    // handleConversationIdInfoChange. Without the dep, the reset click captures a
+    // stale closure over the original handleChangeConversation identity.
+    it('handleNewConversation tracks handleChangeConversation identity', async () => {
+      const { result, rerender } = await renderWithClient(() =>
+        useEmbeddedChatbot(AppSourceType.webApp),
+      )
+
+      const firstHandleNewConversation = result.current.handleNewConversation
+      const firstHandleChangeConversation = result.current.handleChangeConversation
+      expect(typeof firstHandleNewConversation).toBe('function')
+      expect(typeof firstHandleChangeConversation).toBe('function')
+
+      // No-prop rerender: useCallback must short-circuit and preserve identity
+      // because no dependency reference changed.
+      await act(async () => {
+        rerender()
+      })
+
+      expect(result.current.handleNewConversation).toBe(firstHandleNewConversation)
+      expect(result.current.handleChangeConversation).toBe(firstHandleChangeConversation)
+
+      // Flip the resolved userId via the store mock so handleChangeConversation's
+      // identity is invalidated. With the fix, handleNewConversation regenerates
+      // alongside it; without the fix, handleNewConversation would still reference
+      // the stale closure.
+      mockStoreState.embeddedUserId = 'embedded-user-2'
+
+      await act(async () => {
+        rerender()
+      })
+
+      await waitFor(() => {
+        expect(result.current.handleChangeConversation).not.toBe(firstHandleChangeConversation)
+      })
+      expect(result.current.handleNewConversation).not.toBe(firstHandleNewConversation)
+    })
+
     it('handleChangeConversation updates current conversation and refetches chat list', async () => {
       mockStoreState.embeddedConversationId = null
       const { result } = await renderWithClient(() => useEmbeddedChatbot(AppSourceType.webApp))

web/app/components/base/chat/embedded-chatbot/hooks.tsx

@@ -393,6 +393,7 @@ export const useEmbeddedChatbot = (appSourceType: AppSourceType, tryAppId?: stri
   }, [
     isTryApp,
     setShowNewConversationItemInList,
+    handleChangeConversation,
     handleNewConversationInputsChange,
     setClearChatList,
   ])