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/services/messages/markdown_renderer_service.rb

@@ -0,0 +1,64 @@
+class Messages::MarkdownRendererService
+  CHANNEL_RENDERERS = {
+    'Channel::Email' => :render_html,
+    'Channel::WebWidget' => :render_html,
+    'Channel::Telegram' => :render_telegram_html,
+    'Channel::Whatsapp' => :render_whatsapp,
+    'Channel::FacebookPage' => :render_instagram,
+    'Channel::Instagram' => :render_instagram,
+    'Channel::Line' => :render_line,
+    'Channel::TwitterProfile' => :render_plain_text,
+    'Channel::Sms' => :render_plain_text,
+    'Channel::TwilioSms' => :render_plain_text
+  }.freeze
+
+  def initialize(content, channel_type)
+    @content = content
+    @channel_type = channel_type
+  end
+
+  def render
+    return @content if @content.blank?
+
+    renderer_method = CHANNEL_RENDERERS[@channel_type]
+    renderer_method ? send(renderer_method) : @content
+  end
+
+  private
+
+  def commonmarker_doc
+    @commonmarker_doc ||= CommonMarker.render_doc(@content, [:DEFAULT, :STRIKETHROUGH_DOUBLE_TILDE])
+  end
+
+  def render_html
+    markdown_renderer = BaseMarkdownRenderer.new
+    doc = CommonMarker.render_doc(@content, :DEFAULT, [:strikethrough])
+    markdown_renderer.render(doc)
+  end
+
+  def render_telegram_html
+    renderer = Messages::MarkdownRenderers::TelegramRenderer.new
+    doc = CommonMarker.render_doc(@content, [:STRIKETHROUGH_DOUBLE_TILDE], [:strikethrough])
+    renderer.render(doc).gsub(/\n+\z/, '')
+  end
+
+  def render_whatsapp
+    renderer = Messages::MarkdownRenderers::WhatsAppRenderer.new
+    renderer.render(commonmarker_doc).gsub(/\n+\z/, '')
+  end
+
+  def render_instagram
+    renderer = Messages::MarkdownRenderers::InstagramRenderer.new
+    renderer.render(commonmarker_doc).gsub(/\n+\z/, '')
+  end
+
+  def render_line
+    renderer = Messages::MarkdownRenderers::LineRenderer.new
+    renderer.render(commonmarker_doc).gsub(/\n+\z/, '')
+  end
+
+  def render_plain_text
+    renderer = Messages::MarkdownRenderers::PlainTextRenderer.new
+    renderer.render(commonmarker_doc).gsub(/\n+\z/, '')
+  end
+end

app/services/messages/markdown_renderers/base_markdown_renderer.rb

@@ -0,0 +1,39 @@
+class Messages::MarkdownRenderers::BaseMarkdownRenderer < CommonMarker::Renderer
+  def document(_node)
+    out(:children)
+  end
+
+  def paragraph(_node)
+    out(:children)
+    cr
+  end
+
+  def text(node)
+    out(node.string_content)
+  end
+
+  def softbreak(_node)
+    out(' ')
+  end
+
+  def linebreak(_node)
+    out("\n")
+  end
+
+  def strikethrough(_node)
+    out('<del>')
+    out(:children)
+    out('</del>')
+  end
+
+  def method_missing(method_name, node = nil, *args, **kwargs, &)
+    return super unless node.is_a?(CommonMarker::Node)
+
+    out(:children)
+    cr unless %i[text softbreak linebreak].include?(node.type)
+  end
+
+  def respond_to_missing?(_method_name, _include_private = false)
+    true
+  end
+end

app/services/messages/markdown_renderers/instagram_renderer.rb

@@ -0,0 +1,44 @@
+class Messages::MarkdownRenderers::InstagramRenderer < Messages::MarkdownRenderers::BaseMarkdownRenderer
+  def initialize
+    super
+    @list_item_number = 0
+  end
+
+  def strong(_node)
+    out('*', :children, '*')
+  end
+
+  def emph(_node)
+    out('_', :children, '_')
+  end
+
+  def code(node)
+    out(node.string_content)
+  end
+
+  def link(node)
+    out(node.url)
+  end
+
+  def list(node)
+    @list_type = node.list_type
+    @list_item_number = @list_type == :ordered_list ? node.list_start : 0
+    out(:children)
+    cr
+  end
+
+  def list_item(_node)
+    if @list_type == :ordered_list
+      out("#{@list_item_number}. ", :children)
+      @list_item_number += 1
+    else
+      out('- ', :children)
+    end
+    cr
+  end
+
+  def blockquote(_node)
+    out(:children)
+    cr
+  end
+end

app/services/messages/markdown_renderers/line_renderer.rb

@@ -0,0 +1,36 @@
+class Messages::MarkdownRenderers::LineRenderer < Messages::MarkdownRenderers::BaseMarkdownRenderer
+  def strong(_node)
+    out(' *', :children, '* ')
+  end
+
+  def emph(_node)
+    out(' _', :children, '_ ')
+  end
+
+  def code(node)
+    out(' `', node.string_content, '` ')
+  end
+
+  def link(node)
+    out(node.url)
+  end
+
+  def list(_node)
+    out(:children)
+    cr
+  end
+
+  def list_item(_node)
+    out(:children)
+    cr
+  end
+
+  def code_block(node)
+    out(' ```', "\n", node.string_content, '``` ', "\n")
+  end
+
+  def blockquote(_node)
+    out(:children)
+    cr
+  end
+end

app/services/messages/markdown_renderers/plain_text_renderer.rb

@@ -0,0 +1,58 @@
+class Messages::MarkdownRenderers::PlainTextRenderer < Messages::MarkdownRenderers::BaseMarkdownRenderer
+  def initialize
+    super
+    @list_item_number = 0
+  end
+
+  def link(node)
+    out(:children)
+    out(' ', node.url) if node.url.present?
+  end
+
+  def strong(_node)
+    out(:children)
+  end
+
+  def emph(_node)
+    out(:children)
+  end
+
+  def code(node)
+    out(node.string_content)
+  end
+
+  def list(node)
+    @list_type = node.list_type
+    @list_item_number = @list_type == :ordered_list ? node.list_start : 0
+    out(:children)
+    cr
+  end
+
+  def list_item(_node)
+    if @list_type == :ordered_list
+      out("#{@list_item_number}. ", :children)
+      @list_item_number += 1
+    else
+      out('- ', :children)
+    end
+    cr
+  end
+
+  def blockquote(_node)
+    out(:children)
+    cr
+  end
+
+  def code_block(node)
+    out(node.string_content, "\n")
+  end
+
+  def header(_node)
+    out(:children)
+    cr
+  end
+
+  def thematic_break(_node)
+    out("\n")
+  end
+end

app/services/messages/markdown_renderers/telegram_renderer.rb

@@ -0,0 +1,60 @@
+class Messages::MarkdownRenderers::TelegramRenderer < Messages::MarkdownRenderers::BaseMarkdownRenderer
+  def initialize
+    super
+    @list_item_number = 0
+  end
+
+  def strong(_node)
+    out('<strong>', :children, '</strong>')
+  end
+
+  def emph(_node)
+    out('<em>', :children, '</em>')
+  end
+
+  def code(node)
+    out('<code>', node.string_content, '</code>')
+  end
+
+  def link(node)
+    out('<a href="', node.url, '">', :children, '</a>')
+  end
+
+  def strikethrough(_node)
+    out('<del>', :children, '</del>')
+  end
+
+  def blockquote(_node)
+    out('<blockquote>', :children, '</blockquote>')
+  end
+
+  def code_block(node)
+    out('<pre>', node.string_content, '</pre>')
+  end
+
+  def list(node)
+    @list_type = node.list_type
+    @list_item_number = @list_type == :ordered_list ? node.list_start : 0
+    out(:children)
+    cr
+  end
+
+  def list_item(_node)
+    if @list_type == :ordered_list
+      out("#{@list_item_number}. ", :children)
+      @list_item_number += 1
+    else
+      out('• ', :children)
+    end
+    cr
+  end
+
+  def header(_node)
+    out('<strong>', :children, '</strong>')
+    cr
+  end
+
+  def softbreak(_node)
+    out("\n")
+  end
+end

app/services/messages/markdown_renderers/whats_app_renderer.rb

@@ -0,0 +1,32 @@
+class Messages::MarkdownRenderers::WhatsAppRenderer < Messages::MarkdownRenderers::BaseMarkdownRenderer
+  def strong(_node)
+    out('*', :children, '*')
+  end
+
+  def emph(_node)
+    out('_', :children, '_')
+  end
+
+  def code(node)
+    out('`', node.string_content, '`')
+  end
+
+  def link(node)
+    out(node.url)
+  end
+
+  def list(_node)
+    out(:children)
+    cr
+  end
+
+  def list_item(_node)
+    out('- ', :children)
+    cr
+  end
+
+  def blockquote(_node)
+    out('> ', :children)
+    cr
+  end
+end