chore: Replace plain editor with advanced editor (#13071)

# Pull Request Template

## Description

This PR reverts the plain text editor back to the **advanced editor**,
which was previously removed in
[https://github.com/chatwoot/chatwoot/pull/13058](https://github.com/chatwoot/chatwoot/pull/13058).
All channels now use the **ProseMirror editor**, with formatting applied
based on each channel’s configuration.

This PR also fixes issues where **new lines were not properly preserved
during Markdown serialization**, for both:

* `Enter or CMD/Ctrl+enter` (new paragraph)
* `Shift+Enter` (`hard_break`)

Additionally, it resolves related **[Sentry
issue](https://chatwoot-p3.sentry.io/issues/?environment=production&project=4507182691975168&query=is%3Aunresolved%20markdown&referrer=issue-list&statsPeriod=7d)**.

With these changes:

* Line breaks and spacing are now preserved correctly when saving canned
responses.
* When editing a canned response, the content retains the exact spacing
and formatting as saved in editor.
* Canned responses are now correctly converted to plain text where
required and displayed consistently in the canned response list.

### https://github.com/chatwoot/prosemirror-schema/pull/38

---

## Type of change

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?



## 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
- [x] 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/components/widgets/WootWriter/Editor.vue

@@ -55,6 +55,7 @@ import {
   getSelectionCoords,
   calculateMenuPosition,
   getEffectiveChannelType,
+  stripUnsupportedFormatting,
 } from 'dashboard/helper/editorHelper';
 import {
   hasPressedEnterAndNotCmdOrShift,
@@ -131,8 +132,10 @@ const editorMenuOptions = computed(() => {
 
 const createState = (content, placeholder, plugins = [], methods = {}) => {
   const schema = editorSchema.value;
+  // Strip unsupported formatting before parsing to prevent "Token type not supported" errors
+  const sanitizedContent = stripUnsupportedFormatting(content, schema);
   return EditorState.create({
-    doc: new MessageMarkdownTransformer(schema).parse(content),
+    doc: new MessageMarkdownTransformer(schema).parse(sanitizedContent),
     plugins: buildEditor({
       schema,
       placeholder,