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/common.sh

@@ -0,0 +1,84 @@
+#!/bin/bash
+# Common helpers and environment detection
+
+set -euo pipefail
+
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+RED='\033[0;31m'
+CYAN='\033[0;36m'
+BOLD='\033[1m'
+NC='\033[0m'
+
+VERBOSE=true
+LOG_FILE="/tmp/archduino-install.log"
+CURRENT_STEP=0
+TOTAL_STEPS=10
+
+info() { echo -e "${GREEN}[✓]${NC} $1"; }
+warn() { echo -e "${YELLOW}[!]${NC} $1"; }
+error() {
+  echo -e "${RED}[✗]${NC} $1"
+  exit 1
+}
+step() { echo -e "\n${GREEN}━━━ $1 ━━━${NC}"; }
+
+# ── Quiet-mode progress bar ────────────────────────────────────
+draw_progress() {
+  local current=$1
+  local total=$2
+  local label=$3
+  local pct=$((current * 100 / total))
+  local bar_width=40
+  local filled=$((pct * bar_width / 100))
+  local empty=$((bar_width - filled))
+  local bar="" space=""
+  for ((i = 0; i < filled; i++)); do bar+="█"; done
+  for ((i = 0; i < empty; i++)); do space+="░"; done
+  printf "\033[2K\r  ${GREEN}${bar}${NC}${space} %3d%%  ${BOLD}%s${NC}" "$pct" "$label" >&3
+}
+
+begin_quiet_mode() {
+  $IS_WSL && TOTAL_STEPS=11
+  : >"$LOG_FILE"
+
+  # Save real terminal to fd 3/4, redirect everything else to log
+  exec 3>&1 4>&2
+  exec 1>>"$LOG_FILE" 2>&1
+
+  # Override output helpers to talk to the terminal via fd 3
+  step() {
+    CURRENT_STEP=$((CURRENT_STEP + 1))
+    draw_progress "$CURRENT_STEP" "$TOTAL_STEPS" "$1"
+  }
+  info() { :; }
+  warn() { printf "\033[2K\r  ${YELLOW}[!]${NC} %s\n" "$1" >&3; }
+  error() {
+    printf "\033[2K\r  ${RED}[✗]${NC} %s\n" "$1" >&3
+    echo "    See log: $LOG_FILE" >&3
+    exit 1
+  }
+}
+
+end_quiet_mode() {
+  # Restore stdout/stderr
+  exec 1>&3 2>&4
+  exec 3>&- 4>&-
+  echo ""
+}
+
+# ── Detect environment ──────────────────────────────────────────
+IS_WSL=false
+[[ -f /proc/version ]] && grep -qi microsoft /proc/version && IS_WSL=true
+
+IS_ARCH=false
+IS_UBUNTU=false
+if command -v pacman &>/dev/null; then
+  IS_ARCH=true
+  PKG_INSTALL="sudo pacman -S --needed --noconfirm"
+elif command -v apt &>/dev/null; then
+  IS_UBUNTU=true
+  PKG_INSTALL="sudo apt install -y"
+else
+  error "Unsupported distro. Need Arch (pacman) or Ubuntu (apt)."
+fi