chore: Enable Participating tab for conversations (#11714)

## Summary

This PR enables the **Participating** conversation view in the main
sidebar and keeps the behavior aligned with existing conversation views.

## What changed

- Added **Participating** under Conversations in the new sidebar.
- Added a guard in conversation realtime `addConversation` flow so
generic `conversation.created` events are not injected while the user is
on Participating view.
- Added participating route mapping in conversation-list redirect helper
so list redirects resolve correctly to `/participating/conversations`.

## Scope notes

- Kept changes minimal and consistent with current `develop` behavior.
- No additional update-event filtering was added beyond what existing
views already do.

---------


Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>

app/javascript/dashboard/store/modules/conversations/helpers/specs/actionHelpers.spec.js

@@ -1,4 +1,8 @@
-import { isOnMentionsView, isOnFoldersView } from '../actionHelpers';
+import {
+  isOnMentionsView,
+  isOnFoldersView,
+  isOnParticipatingView,
+} from '../actionHelpers';
 
 describe('#isOnMentionsView', () => {
   it('return valid responses when passing the state', () => {
@@ -24,3 +28,19 @@ describe('#isOnFoldersView', () => {
     );
   });
 });
+
+describe('#isOnParticipatingView', () => {
+  it('return valid responses when passing the state', () => {
+    expect(
+      isOnParticipatingView({ route: { name: 'conversation_participating' } })
+    ).toBe(true);
+    expect(
+      isOnParticipatingView({
+        route: { name: 'conversation_through_participating' },
+      })
+    ).toBe(true);
+    expect(
+      isOnParticipatingView({ route: { name: 'conversation_messages' } })
+    ).toBe(false);
+  });
+});