refactor: restructure installation to modular architecture

- Remove monolithic bootstrap.sh in favor of modular design
- Add install.sh as new main entry point with improved UX
- Split functionality into focused modules:
  - lib/common.sh: shared utilities and environment detection
  - lib/packages.sh: base system packages
  - lib/neovim.sh: Neovim and LazyVim setup
  - lib/arduino.sh: Arduino CLI and board cores
  - lib/git.sh: Git and Lazygit configuration
  - lib/shell-config.sh: Zsh and shell environment
  - lib/starship.sh: Starship prompt setup
  - lib/zellij.sh: Zellij terminal multiplexer
  - lib/scaffold.sh: project scaffolding utilities
- Update README with new installation instructions and architecture
- Improve error handling and user feedback across modules
- Maintain compatibility with both Arch Linux and Ubuntu/WSL2

This modular approach enables better maintainability, testing,
and allows users to selectively run components as needed.

lib/neovim.sh

@@ -0,0 +1,107 @@
+#!/bin/bash
+# Steps 5+6: Neovim + NvChad
+
+step "5/9 — Installing Neovim (latest)"
+
+NVIM_NEEDED=true
+if command -v nvim &>/dev/null; then
+  NVIM_VER=$(nvim --version | head -1 | grep -oP '\d+\.\d+\.\d+')
+  if [[ "$(printf '%s\n' "0.11.2" "$NVIM_VER" | sort -V | head -1)" == "0.11.2" ]]; then
+    NVIM_NEEDED=false
+    info "Neovim $NVIM_VER already meets requirements"
+  fi
+fi
+
+if $NVIM_NEEDED; then
+  curl -kLO https://github.com/neovim/neovim/releases/latest/download/nvim-linux-x86_64.tar.gz
+  sudo rm -rf /opt/nvim-linux-x86_64
+  sudo tar -xzf nvim-linux-x86_64.tar.gz -C /opt
+  sudo ln -sf /opt/nvim-linux-x86_64/bin/nvim /usr/local/bin/nvim
+  rm nvim-linux-x86_64.tar.gz
+  info "Neovim installed: $(nvim --version | head -1)"
+fi
+
+step "6/9 — Setting up NvChad"
+
+if [[ ! -d "$HOME/.config/nvim/lua" ]]; then
+  for d in ~/.config/nvim ~/.local/share/nvim ~/.local/state/nvim ~/.cache/nvim; do
+    [[ -d "$d" ]] && mv "$d" "${d}.bak.$(date +%s)"
+  done
+  git clone https://github.com/NvChad/starter ~/.config/nvim
+  rm -rf ~/.config/nvim/.git
+  info "NvChad starter cloned"
+else
+  info "Neovim config already exists, skipping NvChad clone"
+fi
+
+# ── Theme ───────────────────────────────────────────────────────
+mkdir -p ~/.config/nvim/lua
+
+cat >~/.config/nvim/lua/chadrc.lua <<EOF
+---@type ChadrcConfig
+local M = {}
+
+M.base46 = {
+  theme = "$NVCHAD_THEME",
+}
+
+return M
+EOF
+
+# ── Arduino plugin ──────────────────────────────────────────────
+mkdir -p ~/.config/nvim/lua/plugins
+
+cat >~/.config/nvim/lua/plugins/arduino.lua <<'LUA'
+return {
+  {
+    "stevearc/vim-arduino",
+    ft = { "arduino", "cpp", "c" },
+    config = function()
+      vim.g.arduino_use_cli = 1
+      vim.g.arduino_cli_path = "arduino-cli"
+    end,
+  },
+}
+LUA
+
+# ── LSP (clangd) ───────────────────────────────────────────────
+mkdir -p ~/.config/nvim/lua/configs
+
+cat >~/.config/nvim/lua/configs/lspconfig.lua <<'LUA'
+local configs = require "nvchad.configs.lspconfig"
+
+local on_attach = configs.on_attach
+local on_init = configs.on_init
+local capabilities = configs.capabilities
+
+local lspconfig = require "lspconfig"
+
+lspconfig.clangd.setup {
+  on_init = on_init,
+  on_attach = on_attach,
+  capabilities = capabilities,
+  cmd = {
+    "clangd",
+    "--background-index",
+    "--clang-tidy",
+    "--header-insertion=iwyu",
+    "--completion-style=detailed",
+  },
+}
+LUA
+
+# ── Keymaps ─────────────────────────────────────────────────────
+cat >~/.config/nvim/lua/mappings.lua <<'LUA'
+require "nvchad.mappings"
+
+local map = vim.keymap.set
+
+map("n", "<leader>ac", "<cmd>ArduinoChooseBoard<cr>", { desc = "Arduino Choose Board" })
+map("n", "<leader>ap", "<cmd>ArduinoChoosePort<cr>", { desc = "Arduino Choose Port" })
+map("n", "<leader>av", "<cmd>ArduinoVerify<cr>", { desc = "Arduino Verify (compile)" })
+map("n", "<leader>au", "<cmd>ArduinoUpload<cr>", { desc = "Arduino Upload" })
+map("n", "<leader>as", "<cmd>ArduinoSerial<cr>", { desc = "Arduino Serial Monitor" })
+map("n", "<leader>ai", "<cmd>ArduinoInfo<cr>", { desc = "Arduino Board Info" })
+LUA
+
+info "NvChad configured ($THEME_DISPLAY_NAME + Arduino + LSP)"