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>

pnpm-lock.yaml

@@ -20,8 +20,8 @@ importers:
         specifier: 1.2.3
         version: 1.2.3
       '@chatwoot/prosemirror-schema':
-        specifier: 1.2.3
-        version: 1.2.3
+        specifier: 1.2.5
+        version: 1.2.5
       '@chatwoot/utils':
         specifier: ^0.0.51
         version: 0.0.51
@@ -421,8 +421,8 @@ packages:
   '@chatwoot/ninja-keys@1.2.3':
     resolution: {integrity: sha512-xM8d9P5ikDMZm2WbaCTk/TW5HFauylrU3cJ75fq5je6ixKwyhl/0kZbVN/vbbZN4+AUX/OaSIn6IJbtCgIF67g==}
 
-  '@chatwoot/prosemirror-schema@1.2.3':
-    resolution: {integrity: sha512-q/EfirVK9jt8FJAx3Gf6y3LoVadmYVLknbYvPrkUe81WO0f2mkZ/kY2UQgpUISVvOGEkCH4bkfYMp5UQ+Buz3g==}
+  '@chatwoot/prosemirror-schema@1.2.5':
+    resolution: {integrity: sha512-nwi0G17jLiRwIzjjQXr9gTZRcDf5BQzo44XxO6CItfR02W5RExugurvHlpc88R4tUrDtIQHGM2Q2vijvFUNIkA==}
 
   '@chatwoot/utils@0.0.51':
     resolution: {integrity: sha512-WlEmWfOTzR7YZRUWzn5Wpm15/BRudpwqoNckph8TohyDbiim1CP4UZGa+qjajxTbNGLLhtKlm0Xl+X16+5Wceg==}
@@ -4862,7 +4862,7 @@ snapshots:
       hotkeys-js: 3.8.7
       lit: 2.2.6
 
-  '@chatwoot/prosemirror-schema@1.2.3':
+  '@chatwoot/prosemirror-schema@1.2.5':
     dependencies:
       markdown-it-sup: 2.0.0
       prosemirror-commands: 1.6.0