Organize and commit nvim configuration improvements

**Configuration Enhancements:**
- Enable Nerd Font support in init.lua
- Enhanced LSP configuration with better clangd setup
- Improved query driver paths and error handling
- Added support for more filetypes (cmake, tex, etc.)

**Plugin Management:**
- Add GitHub Copilot integration
- Remove experimental plugins (avante, completion, statusline, theme)
- Reorganize plugin imports for better structure

**Repository Maintenance:**
- Update .gitignore for better artifact handling
- Clean up unused plugin configurations
- Establish clean baseline for future development

Resolves #12

lua/custom/plugins/copilot.lua

@@ -0,0 +1,14 @@
+return {
+  {
+    'github/copilot.vim',
+    event = 'VimEnter',
+    config = function()
+      -- Accept suggestion with Ctrl-y
+      vim.keymap.set('i', '<C-y>', 'copilot#Accept("\\<CR>")', {
+        expr = true,
+        replace_keycodes = false
+      })
+      vim.g.copilot_no_tab_map = true
+    end,
+  },
+}