refactor: Complete modular migration from kickstart.nvim

Major architectural overhaul to transform the flat kickstart.nvim structure
  into a maintainable, modular configuration while preserving upstream sync capability.

  ## Structure Changes
  - Migrated from flat `lua/custom/` to organized `lua/core/` and `lua/plugins/`
  - Separated plugin specs from configs: `lua/plugins/spec/` and `lua/plugins/config/`
  - Complex configs (LSP, Debug) now use directory structure with sub-modules:
    - `lsp/init.lua`, `lsp/servers.lua`, `lsp/keymaps.lua`
    - `debug/init.lua`, `debug/adapters.lua`, `debug/keymaps.lua`

  ## Core Improvements
  - Created dedicated core modules: options, keymaps, autocmds, bootstrap, health
  - Added comprehensive health check (`lua/core/health.lua`) for diagnostics
  - Simplified init.lua to just orchestrate module loading
  - Better separation of concerns throughout

  ## Plugin Updates
  - Fixed Blink.cmp configuration (removed invalid fuzzy options)
  - Integrated Copilot with Blink.cmp for unified completion experience
  - Added autopairs and indent-line from kickstart examples
  - Optimized for Nix development environments (removed venv assumptions)

  ## Documentation
  - Updated README with modular structure and kickstart sync instructions
  - Created comprehensive KEYBIND_ANALYSIS.md with all mappings
  - Added modular.txt help documentation
  - Created TODO_TEST.md checklist for testing

  ## Benefits
  - Easier to maintain and extend
  - Clean separation allows upstream kickstart merges without conflicts
  - Scalable architecture for adding new languages/tools
  - Better code organization and discoverability

  All kickstart functionality preserved while gaining modularity and maintainability.

lua/plugins/config/editor.lua

@@ -0,0 +1,59 @@
+-- Editor Enhancement Configuration
+local M = {}
+
+function M.setup_mini()
+  -- Better Around/Inside textobjects
+  require('mini.ai').setup { n_lines = 500 }
+  
+  -- Add/delete/replace surroundings (brackets, quotes, etc.)
+  require('mini.surround').setup()
+  
+  -- Simple and easy statusline
+  local statusline = require 'mini.statusline'
+  statusline.setup { use_icons = vim.g.have_nerd_font }
+  
+  -- Custom statusline location section
+  ---@diagnostic disable-next-line: duplicate-set-field
+  statusline.section_location = function()
+    return '%2l:%-2v'
+  end
+end
+
+function M.setup_illuminate()
+  require('illuminate').configure({
+    delay = 200,
+    large_file_cutoff = 2000,
+    large_file_overrides = {
+      providers = { 'lsp' },
+    },
+    providers = {
+      'lsp',
+      'treesitter',
+      'regex',
+    },
+    filetypes_denylist = {
+      'dirbuf',
+      'dirvish',
+      'fugitive',
+      'alpha',
+      'NvimTree',
+      'lazy',
+      'neogitstatus',
+      'Trouble',
+      'lir',
+      'Outline',
+      'spectre_panel',
+      'toggleterm',
+      'DressingSelect',
+      'TelescopePrompt',
+    },
+    under_cursor = true,
+  })
+end
+
+function M.setup()
+  M.setup_mini()
+  M.setup_illuminate()
+end
+
+return M