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/telescope.lua

@@ -0,0 +1,84 @@
+-- Telescope Configuration
+local M = {}
+
+function M.setup()
+  local telescope = require('telescope')
+  local builtin = require('telescope.builtin')
+  
+  telescope.setup({
+    defaults = {
+      prompt_prefix = '> ',
+      selection_caret = '> ',
+      path_display = { 'truncate' },
+      sorting_strategy = 'ascending',
+      layout_config = {
+        horizontal = {
+          prompt_position = 'top',
+          preview_width = 0.55,
+        },
+        vertical = {
+          mirror = false,
+        },
+        width = 0.87,
+        height = 0.80,
+        preview_cutoff = 120,
+      },
+    },
+    pickers = {
+      find_files = {
+        -- Use rg for finding files (ensure rg is installed via Nix/Home Manager)
+        find_command = { 'rg', '--files', '--hidden', '-g', '!.git' },
+      },
+    },
+    extensions = {
+      ['ui-select'] = {
+        require('telescope.themes').get_dropdown(),
+      },
+      fzf = {
+        fuzzy = true,
+        override_generic_sorter = true,
+        override_file_sorter = true,
+        case_mode = 'smart_case',
+      },
+    },
+  })
+  
+  -- Load extensions
+  pcall(telescope.load_extension, 'fzf')
+  pcall(telescope.load_extension, 'ui-select')
+  
+  -- Setup keymaps
+  vim.keymap.set('n', '<leader>sf', builtin.find_files, { desc = '[S]earch [F]iles' })
+  vim.keymap.set('n', '<leader>sg', builtin.live_grep, { desc = '[S]earch by [G]rep' })
+  vim.keymap.set('n', '<leader>sh', builtin.help_tags, { desc = '[S]earch [H]elp' })
+  vim.keymap.set('n', '<leader>sk', builtin.keymaps, { desc = '[S]earch [K]eymaps' })
+  vim.keymap.set('n', '<leader>ss', builtin.builtin, { desc = '[S]earch [S]elect Telescope' })
+  vim.keymap.set('n', '<leader>sw', builtin.grep_string, { desc = '[S]earch current [W]ord' })
+  vim.keymap.set('n', '<leader>sd', builtin.diagnostics, { desc = '[S]earch [D]iagnostics' })
+  vim.keymap.set('n', '<leader>sr', builtin.resume, { desc = '[S]earch [R]esume' })
+  vim.keymap.set('n', '<leader>s.', builtin.oldfiles, { desc = '[S]earch Recent Files ("." for repeat)' })
+  vim.keymap.set('n', '<leader><leader>', builtin.buffers, { desc = '[ ] Find existing buffers' })
+  
+  -- Fuzzy search in current buffer
+  vim.keymap.set('n', '<leader>/', function()
+    builtin.current_buffer_fuzzy_find(require('telescope.themes').get_dropdown {
+      winblend = 10,
+      previewer = false,
+    })
+  end, { desc = '[/] Fuzzily search in current buffer' })
+  
+  -- Search in open files
+  vim.keymap.set('n', '<leader>s/', function()
+    builtin.live_grep {
+      grep_open_files = true,
+      prompt_title = 'Live Grep in Open Files',
+    }
+  end, { desc = '[S]earch [/] in Open Files' })
+  
+  -- Search in neovim config
+  vim.keymap.set('n', '<leader>sn', function()
+    builtin.find_files { cwd = vim.fn.stdpath 'config' }
+  end, { desc = '[S]earch [N]eovim files' })
+end
+
+return M