feat: initial Phase 1 PoC scaffolding for KubeSolo OS

Complete Phase 1 implementation of KubeSolo OS — an immutable, bootable
Linux distribution built on Tiny Core Linux for running KubeSolo
single-node Kubernetes.

Build system:
- Makefile with fetch, rootfs, initramfs, iso, disk-image targets
- Dockerfile.builder for reproducible builds
- Scripts to download Tiny Core, extract rootfs, inject KubeSolo,
  pack initramfs, and create bootable ISO/disk images

Init system (10 POSIX sh stages):
- Early mount (proc/sys/dev/cgroup2), cmdline parsing, persistent
  mount with bind-mounts, kernel module loading, sysctl, DHCP
  networking, hostname, clock sync, containerd prep, KubeSolo exec

Shared libraries:
- functions.sh (device wait, IP lookup, config helpers)
- network.sh (static IP, config persistence, interface detection)
- health.sh (containerd, API server, node readiness checks)
- Emergency shell for boot failure debugging

Testing:
- QEMU boot test with serial log marker detection
- K8s readiness test with kubectl verification
- Persistence test (reboot + verify state survives)
- Workload deployment test (nginx pod)
- Local storage test (PVC + local-path provisioner)
- Network policy test
- Reusable run-vm.sh launcher

Developer tools:
- dev-vm.sh (interactive QEMU with port forwarding)
- rebuild-initramfs.sh (fast iteration)
- inject-ssh.sh (dropbear SSH for debugging)
- extract-kernel-config.sh + kernel-audit.sh

Documentation:
- Full design document with architecture research
- Boot flow documentation covering all 10 init stages
- Cloud-init examples (DHCP, static IP, Portainer Edge, air-gapped)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

init/lib/functions.sh

@@ -0,0 +1,75 @@
+#!/bin/sh
+# functions.sh — Shared utility functions for KubeSolo OS init
+# Sourced by /sbin/init before running stages
+# POSIX sh only — must work with BusyBox ash
+
+# Wait for a block device to appear
+wait_for_device() {
+    dev="$1"
+    timeout="${2:-30}"
+    i=0
+    while [ "$i" -lt "$timeout" ]; do
+        [ -b "$dev" ] && return 0
+        sleep 1
+        i=$((i + 1))
+    done
+    return 1
+}
+
+# Wait for a file to appear
+wait_for_file() {
+    path="$1"
+    timeout="${2:-30}"
+    i=0
+    while [ "$i" -lt "$timeout" ]; do
+        [ -f "$path" ] && return 0
+        sleep 1
+        i=$((i + 1))
+    done
+    return 1
+}
+
+# Get IP address of an interface (POSIX-safe, no grep -P)
+get_iface_ip() {
+    iface="$1"
+    ip -4 addr show "$iface" 2>/dev/null | \
+        sed -n 's/.*inet \([0-9.]*\).*/\1/p' | head -1
+}
+
+# Check if running in a VM (useful for adjusting timeouts)
+is_virtual() {
+    [ -d /sys/class/dmi/id ] && \
+        grep -qi -e 'qemu' -e 'kvm' -e 'vmware' -e 'virtualbox' -e 'xen' -e 'hyperv' \
+            /sys/class/dmi/id/sys_vendor 2>/dev/null
+}
+
+# Resolve a LABEL= or UUID= device spec to a block device path
+resolve_device() {
+    spec="$1"
+    case "$spec" in
+        LABEL=*) blkid -L "${spec#LABEL=}" 2>/dev/null ;;
+        UUID=*)  blkid -U "${spec#UUID=}" 2>/dev/null ;;
+        *)       echo "$spec" ;;
+    esac
+}
+
+# Write a key=value pair to a simple config file
+config_set() {
+    file="$1" key="$2" value="$3"
+    if grep -q "^${key}=" "$file" 2>/dev/null; then
+        sed -i "s|^${key}=.*|${key}=${value}|" "$file"
+    else
+        echo "${key}=${value}" >> "$file"
+    fi
+}
+
+# Read a value from a simple key=value config file
+config_get() {
+    file="$1" key="$2" default="${3:-}"
+    if [ -f "$file" ]; then
+        value=$(sed -n "s/^${key}=//p" "$file" | tail -1)
+        echo "${value:-$default}"
+    else
+        echo "$default"
+    fi
+}