Add container runtime pre-flight check

Validates Docker or Podman is installed and running before attempting
to build the devcontainer. Aborts with OS-specific remediation guidance
(Windows/WSL, macOS, Linux) instead of a cryptic Docker client error.

Author: AnExiledDev

.devcontainer/CHANGELOG.md

@@ -4,6 +4,9 @@
 
 ### Added
 
+#### Startup
+- **Container runtime pre-flight check** — validates Docker or Podman is installed and running before attempting to build the devcontainer; aborts with OS-specific remediation guidance (Windows/WSL, macOS, Linux) instead of a cryptic Docker client error
+
 #### README
 - **"Why CodeForge?" section** — motivation and value proposition explaining the project's origins as a power user's personal setup
 - **Architecture overview** — three-layer diagram (DevContainer → CodeForge Layer → Claude Code) with brief descriptions and link to full architecture docs

.devcontainer/devcontainer.json

@@ -5,6 +5,8 @@
 	"workspaceFolder": "/workspaces",
 	"workspaceMount": "source=${localWorkspaceFolder},target=/workspaces,type=bind",
 
+	"initializeCommand": "bash .devcontainer/scripts/preflight.sh",
+
 	"mounts": [
 		{
 			"source": "codeforge-claude-config-${devcontainerId}",

.devcontainer/scripts/preflight.sh

@@ -0,0 +1,113 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: GPL-3.0-only
+# Copyright (c) 2026 Marcus Krueger
+# Pre-flight check: validates a container runtime is available on the host.
+# Runs via initializeCommand BEFORE any container build/pull/start.
+
+set -euo pipefail
+
+# --- OS detection ---
+
+detect_os() {
+    if [[ -f /proc/version ]] && grep -qi 'microsoft\|wsl' /proc/version 2>/dev/null; then
+        echo "wsl"
+    elif [[ "$(uname -s)" == "Darwin" ]]; then
+        echo "macos"
+    else
+        echo "linux"
+    fi
+}
+
+# --- Timeout wrapper (macOS lacks coreutils timeout) ---
+
+run_with_timeout() {
+    local seconds="$1"
+    shift
+    if command -v timeout &>/dev/null; then
+        timeout "$seconds" "$@" &>/dev/null 2>&1
+    else
+        # Fallback for macOS: background + kill
+        "$@" &>/dev/null 2>&1 &
+        local pid=$!
+        (sleep "$seconds" && kill "$pid" 2>/dev/null) &
+        local watchdog=$!
+        if wait "$pid" 2>/dev/null; then
+            kill "$watchdog" 2>/dev/null
+            wait "$watchdog" 2>/dev/null
+            return 0
+        else
+            kill "$watchdog" 2>/dev/null
+            wait "$watchdog" 2>/dev/null
+            return 1
+        fi
+    fi
+}
+
+# --- Runtime detection ---
+
+check_runtime() {
+    local runtime="$1"
+    if ! command -v "$runtime" &>/dev/null; then
+        return 1
+    fi
+    if run_with_timeout 5 "$runtime" info; then
+        return 0
+    fi
+    return 1
+}
+
+# --- Main ---
+
+for runtime in docker podman; do
+    if check_runtime "$runtime"; then
+        exit 0
+    fi
+done
+
+# No working runtime found — determine why and advise
+
+found_binary=""
+for runtime in docker podman; do
+    if command -v "$runtime" &>/dev/null; then
+        found_binary="$runtime"
+        break
+    fi
+done
+
+HOST_OS="$(detect_os)"
+
+echo ""
+echo "╔══════════════════════════════════════════════════════════════╗"
+echo "║  CodeForge: Container runtime not available                 ║"
+echo "╚══════════════════════════════════════════════════════════════╝"
+echo ""
+
+if [[ -n "$found_binary" ]]; then
+    echo "  Found '$found_binary' but the daemon is not responding."
+    echo ""
+    case "$HOST_OS" in
+        wsl)
+            echo "  Fix: Start Docker Desktop and enable WSL 2 integration:"
+            echo "        Settings → Resources → WSL Integration"
+            ;;
+        macos)
+            echo "  Fix: Start Docker Desktop:"
+            echo "        open -a Docker"
+            ;;
+        linux)
+            echo "  Fix: Start the Docker daemon:"
+            echo "        sudo systemctl start docker"
+            ;;
+    esac
+else
+    echo "  No container runtime (docker or podman) found in PATH."
+    echo ""
+    echo "  Install Docker Desktop:"
+    echo "    https://www.docker.com/products/docker-desktop/"
+    echo ""
+    echo "  Or install Podman:"
+    echo "    https://podman.io/getting-started/installation"
+fi
+
+echo ""
+exit 1