Add diagnostic severity highlighting for quickfix lists

Enhance visibility of diagnostic messages in quickfix and location
lists by adding custom syntax groups for error, warning, info,
hint, and note.

lua/autocmds.lua

@@ -76,5 +76,27 @@ vim.api.nvim_create_autocmd("FileType", {
   end,
 })
 
+-- Phase 11.8: Colorize diagnostic severity in quickfix/location list
+vim.api.nvim_create_autocmd("FileType", {
+  group = aug,
+  pattern = "qf",  -- Applies to both quickfix and location list
+  callback = function()
+    -- Use matchadd() for higher priority highlighting
+    -- This will override the default qf syntax
+    vim.fn.matchadd('qfError', '\\<error\\>', 10)
+    vim.fn.matchadd('qfWarning', '\\<warning\\>', 10)
+    vim.fn.matchadd('qfInfo', '\\<info\\>', 10)
+    vim.fn.matchadd('qfHint', '\\<hint\\>', 10)
+    vim.fn.matchadd('qfNote', '\\<note\\>', 10)
+    
+    -- Also match uppercase variants
+    vim.fn.matchadd('qfError', '\\<Error\\>', 10)
+    vim.fn.matchadd('qfWarning', '\\<Warning\\>', 10)
+    vim.fn.matchadd('qfInfo', '\\<Info\\>', 10)
+    vim.fn.matchadd('qfHint', '\\<Hint\\>', 10)
+    vim.fn.matchadd('qfNote', '\\<Note\\>', 10)
+  end,
+})
+
 return {}
 

lua/paper-tonic-modern/groups/editor.lua

@@ -118,11 +118,19 @@ return {
   Conceal = 'Noise',
   
   -- ============================================================================
-  -- QuickFix
+  -- QuickFix & Location List
   -- ============================================================================
   
   QuickFixLine = { bg = c.bg_hl_special_weak, bold = true },
   
+  -- Diagnostic severity highlighting in quickfix/location list
+  -- These are custom syntax groups defined in autocmds.lua
+  qfError = { fg = c.diag_error, bold = true },      -- "error:" or "[E]"
+  qfWarning = { fg = c.diag_warn, bold = true },     -- "warning:" or "[W]"
+  qfInfo = { fg = c.diag_info, bold = true },        -- "info:" or "[I]"
+  qfHint = { fg = c.diag_hint, bold = true },        -- "hint:" or "[H]"
+  qfNote = { fg = c.diag_hint, bold = true },        -- "note:" (same as hint)
+  
   -- ============================================================================
   -- Debug
   -- ============================================================================