feat: improve chat buffer syntax highlighting

Add dedicated highlight group for input contexts and update existing highlight
groups to better organize visual elements in the chat buffer. CopilotChatSpinner
is now renamed to CopilotChatStatus for better semantics. Syntax matching is
improved to handle input contexts with proper containment rules.

Author: deathbeam

README.md

@@ -619,12 +619,13 @@ vim.api.nvim_create_autocmd('BufEnter', {
 
 Types of copilot highlights:
 
-- `CopilotChatSpinner` - Spinner in chat buffer
+- `CopilotChatHeader` - Header highlight in chat buffer
+- `CopilotChatSeparator` - Separator highlight in chat buffer
+- `CopilotChatStatus` - Status and spinner in chat buffer
 - `CopilotChatHelp` - Help messages in chat buffer (help, references)
 - `CopilotChatSelection` - Selection highlight in source buffer
 - `CopilotChatKeyword` - Keyword highlight in chat buffer (e.g. prompts, contexts)
-- `CopilotChatHeader` - Header highlight in chat buffer
-- `CopilotChatSeparator` - Separator highlight in chat buffer
+- `CopilotChatInput` - Input highlight in chat buffer (for contexts)
 
 # API Reference
 

lua/CopilotChat/init.lua

@@ -44,9 +44,14 @@ local function update_highlights()
   M.complete_items(function(items)
     for _, item in ipairs(items) do
       local pattern = vim.fn.escape(item.word, '.-$^*[]')
-      vim.cmd.syntax('match CopilotChatKeyword "' .. pattern .. '"')
+      if vim.startswith(item.word, '#') then
+        vim.cmd('syntax match CopilotChatKeyword "' .. pattern .. '\\(:.\\+\\)\\?" containedin=ALL')
+      else
+        vim.cmd('syntax match CopilotChatKeyword "' .. pattern .. '" containedin=ALL')
+      end
     end
 
+    vim.cmd('syntax match CopilotChatInput ":\\(.\\+\\)" contained containedin=CopilotChatKeyword')
     state.highlights_loaded = true
   end)
 end
@@ -870,10 +875,11 @@ function M.setup(config)
     M.log_level(M.config.log_level)
   end
 
-  vim.api.nvim_set_hl(0, 'CopilotChatSpinner', { link = 'DiagnosticHint', default = true })
+  vim.api.nvim_set_hl(0, 'CopilotChatStatus', { link = 'DiagnosticHint', default = true })
   vim.api.nvim_set_hl(0, 'CopilotChatHelp', { link = 'DiagnosticInfo', default = true })
-  vim.api.nvim_set_hl(0, 'CopilotChatSelection', { link = 'Visual', default = true })
   vim.api.nvim_set_hl(0, 'CopilotChatKeyword', { link = 'Keyword', default = true })
+  vim.api.nvim_set_hl(0, 'CopilotChatInput', { link = 'Special', default = true })
+  vim.api.nvim_set_hl(0, 'CopilotChatSelection', { link = 'Visual', default = true })
   vim.api.nvim_set_hl(
     0,
     'CopilotChatHeader',

lua/CopilotChat/ui/spinner.lua

@@ -63,7 +63,7 @@ function Spinner:start()
           hl_mode = 'combine',
           priority = 100,
           virt_text = {
-            { frame, 'CopilotChatSpinner' },
+            { frame, 'CopilotChatStatus' },
           },
         }
       )