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/lsp/init.lua

@@ -0,0 +1,26 @@
+-- LSP Configuration Module
+local M = {}
+
+function M.setup()
+  local lspconfig = require 'lspconfig'
+  
+  -- Get capabilities from blink.cmp if available
+  local capabilities = {}
+  pcall(function()
+    capabilities = require('blink.cmp').get_lsp_capabilities()
+  end)
+  
+  -- Load server configurations
+  local servers = require('plugins.config.lsp.servers').get_servers()
+  
+  -- Setup each server with capabilities
+  for name, config in pairs(servers) do
+    config.capabilities = vim.tbl_deep_extend('force', {}, capabilities, config.capabilities or {})
+    lspconfig[name].setup(config)
+  end
+  
+  -- Setup LSP keymaps
+  require('plugins.config.lsp.keymaps').setup()
+end
+
+return M

lua/plugins/config/lsp/keymaps.lua

@@ -0,0 +1,57 @@
+-- LSP Keymaps Configuration
+local M = {}
+
+function M.setup()
+  -- Setup keymaps when LSP attaches to a buffer
+  vim.api.nvim_create_autocmd('LspAttach', {
+    group = vim.api.nvim_create_augroup('lsp-attach-keymaps', { clear = true }),
+    callback = function(event)
+      -- Helper function to define keymaps
+      local map = function(keys, func, desc, mode)
+        mode = mode or 'n'
+        vim.keymap.set(mode, keys, func, { buffer = event.buf, desc = 'LSP: ' .. desc })
+      end
+
+      -- Navigation keymaps (using kickstart.nvim patterns)
+      map('gd', require('telescope.builtin').lsp_definitions, '[G]oto [D]efinition')
+      map('grr', require('telescope.builtin').lsp_references, '[G]oto [R]eferences')
+      map('gri', require('telescope.builtin').lsp_implementations, '[G]oto [I]mplementation')
+      map('grt', require('telescope.builtin').lsp_type_definitions, '[G]oto [T]ype definition')
+      map('grD', vim.lsp.buf.declaration, '[G]oto [D]eclaration')
+      
+      -- Symbol operations
+      map('grn', vim.lsp.buf.rename, '[G]oto [R]e[n]ame')
+      map('gra', vim.lsp.buf.code_action, '[G]oto code [A]ction', { 'n', 'x' })
+      map('gO', require('telescope.builtin').lsp_document_symbols, '[G]oto [O]pen document symbols')
+      map('gW', require('telescope.builtin').lsp_dynamic_workspace_symbols, '[G]oto [W]orkspace symbols')
+      
+      -- Documentation
+      map('K', vim.lsp.buf.hover, 'Hover Documentation')
+      
+      -- Formatting
+      map('<leader>f', function()
+        vim.lsp.buf.format { async = true }
+      end, '[F]ormat buffer')
+      
+      -- The following keymaps are available but not mapped by default:
+      -- vim.lsp.buf.signature_help - Show function signature help
+      -- vim.lsp.buf.add_workspace_folder - Add workspace folder
+      -- vim.lsp.buf.remove_workspace_folder - Remove workspace folder
+      -- vim.lsp.buf.list_workspace_folders - List workspace folders
+      
+      -- Optional: Add a message when LSP attaches
+      local client = vim.lsp.get_client_by_id(event.data.client_id)
+      if client then
+        vim.notify('LSP attached: ' .. client.name, vim.log.levels.INFO)
+      end
+    end,
+  })
+  
+  -- Diagnostic keymaps (available globally, not just when LSP attaches)
+  vim.keymap.set('n', '[d', vim.diagnostic.goto_prev, { desc = 'Go to previous [D]iagnostic message' })
+  vim.keymap.set('n', ']d', vim.diagnostic.goto_next, { desc = 'Go to next [D]iagnostic message' })
+  vim.keymap.set('n', '<leader>e', vim.diagnostic.open_float, { desc = 'Show diagnostic [E]rror messages' })
+  vim.keymap.set('n', '<leader>q', vim.diagnostic.setloclist, { desc = 'Open diagnostic [Q]uickfix list' })
+end
+
+return M

lua/plugins/config/lsp/servers.lua

@@ -0,0 +1,88 @@
+-- LSP Server Configurations
+local M = {}
+
+local util = require 'lspconfig.util'
+
+-- Query driver for clangd to find compilers in various locations
+local function get_clangd_query_driver()
+  return table.concat({
+    '/nix/store/*/bin/clang*',
+    '/opt/homebrew/opt/llvm/bin/clang*',
+    '/usr/bin/clang*',
+  }, ';')
+end
+
+-- Get clang resource directory
+local function get_clang_resource_dir()
+  local ok, result = pcall(vim.fn.systemlist, { 'clang++', '--print-resource-dir' })
+  if ok and result and result[1] then
+    return result[1]
+  else
+    return '/usr/lib/clang/19/include' -- fallback
+  end
+end
+
+function M.get_servers()
+  return {
+    -- C/C++ Language Server
+    clangd = {
+      cmd = {
+        'clangd',
+        '--background-index',
+        '--clang-tidy',
+        '--header-insertion=never',
+        '--query-driver=' .. get_clangd_query_driver(),
+        '--compile-commands-dir=build',
+        '--resource-dir=' .. get_clang_resource_dir(),
+      },
+      filetypes = { 'c', 'cpp', 'objc', 'objcpp', 'cuda' },
+      root_dir = util.root_pattern('CMakeLists.txt', '.git'),
+      single_file_support = true,
+    },
+
+    -- Python Language Server
+    pyright = {
+      settings = {
+        python = {
+          analysis = {
+            autoSearchPaths = true,
+            diagnosticMode = 'openFilesOnly',
+            useLibraryCodeForTypes = true,
+            typeCheckingMode = 'basic',
+          },
+        },
+      },
+      positionEncoding = 'utf-8',
+    },
+    
+    -- Python Linter/Formatter
+    ruff = {},
+    
+    -- Nix Language Server
+    nixd = {},
+    
+    -- LaTeX Language Server
+    texlab = {},
+    
+    -- CMake Language Server
+    cmake = {
+      cmd = { 'cmake-language-server' },
+      filetypes = { 'cmake' },
+      root_dir = util.root_pattern('CMakeLists.txt', '.git'),
+    },
+    
+    -- Add more servers here as needed
+    -- Example:
+    -- rust_analyzer = {
+    --   settings = {
+    --     ['rust-analyzer'] = {
+    --       checkOnSave = {
+    --         command = 'clippy',
+    --       },
+    --     },
+    --   },
+    -- },
+  }
+end
+
+return M