fix: Prevent article editor from resetting content while typing (#14014)

# Pull Request Template

## Description


### Description

This PR fixes an issue where the editor would reset content and move the
cursor while typing. The issue was caused by a dual debounce setup
(400ms + 2500ms) that saved content and then overwrote local state with
stale API responses while the user was still typing.

### What changed

* Editor now uses local state (`localTitle`, `localContent`) as the
source of truth while editing
* Vuex store is only used on initial load or navigation
* Replaced dual debounce with a single 500ms debounce (fewer API calls)
* `UPDATE_ARTICLE` now merges updates instead of replacing the article
  * Prevents status changes from wiping unsaved content
* Removed `updateAsync` for a simpler update flow

### How it works

User types
→ local ref updates immediately (editor reads from this)
→ 500ms debounce triggers
→ dispatches `articles/update`
→ API persists the change
→ on success: store merges the response (used by other components)
→ editor remains unaffected (continues using local state)



Fixes
https://linear.app/chatwoot/issue/CW-6727/better-syncing-of-content-the-editor-randomly-updates-the-content

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

1. Open any Help Center article for editing
2. Type continuously for a few seconds — content should not reset or
jump
3. Change article status (publish/archive/draft) while editing — content
should remain intact
4. Test on a slow network (use DevTools throttling) — typing should
remain smooth


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/javascript/dashboard/store/modules/helpCenterArticles/mutations.js

@@ -79,14 +79,12 @@ export const mutations = {
   [types.UPDATE_ARTICLE]: ($state, updatedArticle) => {
     const articleId = updatedArticle.id;
     if ($state.articles.byId[articleId]) {
-      // Preserve the original position
-      const originalPosition = $state.articles.byId[articleId].position;
+      const existing = $state.articles.byId[articleId];
 
-      // Update the article, keeping the original position
-      // This is not moved out of the original position when we update the article
       $state.articles.byId[articleId] = {
+        ...existing,
         ...updatedArticle,
-        position: originalPosition,
+        position: existing.position,
       };
     }
   },