feat: Standardize rich editor across all channels (#12600)

# Pull Request Template

## Description

This PR includes,

1. **Channel-specific formatting and menu options** for the rich reply
editor.
2. **Removal of the plain reply editor** and full **standardization** on
the rich reply editor across all channels.
3. **Fix for multiple canned responses insertion:**
* **Before:** The plain editor only allowed inserting canned responses
at the beginning of a message, making it impossible to combine multiple
canned responses in a single reply. This caused inconsistent behavior
across the app.
* **Solution:** Replaced the plain reply editor with the rich
(ProseMirror) editor to ensure a unified experience. Agents can now
insert multiple canned responses at any cursor position.
4. **Floating editor menu** for the reply box to improve accessibility
and overall user experience.
5. **New Strikethrough formatting option** added to the editor menu.

---

**Editor repo PR**:
https://github.com/chatwoot/prosemirror-schema/pull/36

Fixes https://github.com/chatwoot/chatwoot/issues/12517,
[CW-5924](https://linear.app/chatwoot/issue/CW-5924/standardize-the-editor),
[CW-5679](https://linear.app/chatwoot/issue/CW-5679/allow-inserting-multiple-canned-responses-in-a-single-message)

## Type of change

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

## How Has This Been Tested?

### Screenshot
**Dark**
<img width="850" height="345" alt="image"
src="https://github.com/user-attachments/assets/47748e6c-380f-44a3-9e3b-c27e0c830bd0"
/>

**Light**
<img width="850" height="345" alt="image"
src="https://github.com/user-attachments/assets/6746cf32-bf63-4280-a5bd-bbd42c3cbe84"
/>


## 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>
Co-authored-by: Pranav <pranav@chatwoot.com>
Co-authored-by: Vinay Keerthi <11478411+stonecharioteer@users.noreply.github.com>

app/javascript/dashboard/helper/editorHelper.js

@@ -5,6 +5,7 @@ import {
 } from '@chatwoot/prosemirror-schema';
 import { replaceVariablesInMessage } from '@chatwoot/utils';
 import * as Sentry from '@sentry/vue';
+import { FORMATTING } from 'dashboard/constants/editor';
 
 /**
  * The delimiter used to separate the signature from the rest of the body.
@@ -314,7 +315,7 @@ const createNode = (editorView, nodeType, content) => {
       return mentionNode;
     }
     case 'cannedResponse':
-      return new MessageMarkdownTransformer(messageSchema).parse(content);
+      return new MessageMarkdownTransformer(state.schema).parse(content);
     case 'variable':
       return state.schema.text(`{{${content}}}`);
     case 'emoji':
@@ -389,3 +390,85 @@ export const getContentNode = (
     ? creator(editorView, content, from, to, variables)
     : { node: null, from, to };
 };
+
+/**
+ * Get the formatting configuration for a specific channel type.
+ * Returns the appropriate marks, nodes, and menu items for the editor.
+ *
+ * @param {string} channelType - The channel type (e.g., 'Channel::FacebookPage', 'Channel::WebWidget')
+ * @returns {Object} The formatting configuration with marks, nodes, and menu properties
+ */
+export function getFormattingForEditor(channelType) {
+  return FORMATTING[channelType] || FORMATTING['Context::Default'];
+}
+
+/**
+ * Menu Positioning Helpers
+ * Handles floating menu bar positioning for text selection in the editor.
+ */
+
+const MENU_CONFIG = { H: 46, W: 300, GAP: 10 };
+
+/**
+ * Calculate selection coordinates with bias to handle line-wraps correctly.
+ * @param {EditorView} editorView - ProseMirror editor view
+ * @param {Selection} selection - Current text selection
+ * @param {DOMRect} rect - Container bounding rect
+ * @returns {{start: Object, end: Object, selTop: number, onTop: boolean}}
+ */
+export function getSelectionCoords(editorView, selection, rect) {
+  const start = editorView.coordsAtPos(selection.from, 1);
+  const end = editorView.coordsAtPos(selection.to, -1);
+
+  const selTop = Math.min(start.top, end.top);
+  const spaceAbove = selTop - rect.top;
+  const onTop =
+    spaceAbove > MENU_CONFIG.H + MENU_CONFIG.GAP || end.bottom > rect.bottom;
+
+  return { start, end, selTop, onTop };
+}
+
+/**
+ * Calculate anchor position based on selection visibility and RTL direction.
+ * @param {Object} coords - Selection coordinates from getSelectionCoords
+ * @param {DOMRect} rect - Container bounding rect
+ * @param {boolean} isRtl - Whether text direction is RTL
+ * @returns {number} Anchor x-position for menu
+ */
+export function getMenuAnchor(coords, rect, isRtl) {
+  const { start, end, onTop } = coords;
+
+  if (!onTop) return end.left;
+
+  // If start of selection is visible, align to text. Else stick to container edge.
+  if (start.top >= rect.top) return isRtl ? start.right : start.left;
+
+  return isRtl ? rect.right - MENU_CONFIG.GAP : rect.left + MENU_CONFIG.GAP;
+}
+
+/**
+ * Calculate final menu position (left, top) within container bounds.
+ * @param {Object} coords - Selection coordinates from getSelectionCoords
+ * @param {DOMRect} rect - Container bounding rect
+ * @param {boolean} isRtl - Whether text direction is RTL
+ * @returns {{left: number, top: number, width: number}}
+ */
+export function calculateMenuPosition(coords, rect, isRtl) {
+  const { start, end, selTop, onTop } = coords;
+
+  const anchor = getMenuAnchor(coords, rect, isRtl);
+
+  // Calculate Left: shift by width if RTL, then make relative to container
+  const rawLeft = (isRtl ? anchor - MENU_CONFIG.W : anchor) - rect.left;
+
+  // Ensure menu stays within container bounds
+  const left = Math.min(Math.max(0, rawLeft), rect.width - MENU_CONFIG.W);
+
+  // Calculate Top: align to selection or bottom of selection
+  const top = onTop
+    ? Math.max(-26, selTop - rect.top - MENU_CONFIG.H - MENU_CONFIG.GAP)
+    : Math.max(start.bottom, end.bottom) - rect.top + MENU_CONFIG.GAP;
+  return { left, top, width: MENU_CONFIG.W };
+}
+
+/* End Menu Positioning Helpers */