Add option to disable header highlighting

Good with plugins like render-markdown.nvim

Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

Author: deathbeam

README.md

@@ -241,6 +241,7 @@ Also see [here](/lua/CopilotChat/config.lua):
   answer_header = '## Copilot ', -- Header to use for AI answers
   error_header = '## Error ', -- Header to use for errors
   separator = '───', -- Separator to use in chat
+  highlight_headers = true, -- Highlight headers in chat, disable if using markdown renderers (like render-markdown.nvim)
 
   show_folds = true, -- Shows folds for sections in chat
   show_help = true, -- Shows help message as virtual lines when waiting for user input
@@ -546,9 +547,16 @@ require('CopilotChat').setup({
 Requires [render-markdown](https://github.com/MeanderingProgrammer/render-markdown.nvim) plugin to be installed.
 
 ```lua
+-- Registers copilot-chat filetype for markdown rendering
 require('render-markdown').setup({
   file_types = { 'markdown', 'copilot-chat' },
 })
+
+-- You might also want to disable default header highlighting for copilot chat when doing this
+require('CopilotChat').setup({
+  highlight_headers = false,
+  -- rest of your config
+})
 ```
 
 ![image](https://github.com/user-attachments/assets/d8dc16f8-3f61-43fa-bfb9-83f240ae30e8)

lua/CopilotChat/chat.lua

@@ -40,6 +40,7 @@ local Chat = class(function(self, help, auto_insert, on_buf_create)
   self.spinner = nil
   self.separator = nil
   self.auto_follow_cursor = true
+  self.highlight_headers = true
   self.layout = nil
 
   vim.treesitter.language.register('markdown', 'copilot-chat')
@@ -72,9 +73,10 @@ function Chat:visible()
 end
 
 function Chat:render()
-  if not self:visible() then
+  if not self.highlight_headers or not self:visible() then
     return
   end
+
   vim.api.nvim_buf_clear_namespace(self.bufnr, self.header_ns, 0, -1)
   local lines = vim.api.nvim_buf_get_lines(self.bufnr, 0, -1, false)
   for l, line in ipairs(lines) do
@@ -219,6 +221,7 @@ function Chat:open(config)
   self.layout = layout
   self.separator = config.separator
   self.auto_follow_cursor = config.auto_follow_cursor
+  self.highlight_headers = config.highlight_headers
 
   vim.wo[self.winnr].wrap = true
   vim.wo[self.winnr].linebreak = true

lua/CopilotChat/config.lua

@@ -104,6 +104,7 @@ return {
   answer_header = '## Copilot ', -- Header to use for AI answers
   error_header = '## Error ', -- Header to use for errors
   separator = '───', -- Separator to use in chat
+  highlight_headers = true, -- Highlight headers in chat, disable if using markdown renderers (like render-markdown.nvim)
 
   show_folds = true, -- Shows folds for sections in chat
   show_help = true, -- Shows help message as virtual lines when waiting for user input