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/50-network.sh

@@ -0,0 +1,64 @@
+#!/bin/sh
+# 50-network.sh — Configure networking
+# Priority: persistent config > cloud-init > DHCP fallback
+
+# Check for saved network config (from previous boot or cloud-init)
+if [ -f "$DATA_MOUNT/network/interfaces.sh" ]; then
+    log "Applying saved network configuration"
+    . "$DATA_MOUNT/network/interfaces.sh"
+    return 0
+fi
+
+# Check for cloud-init network config
+CLOUDINIT_FILE="${KUBESOLO_CLOUDINIT:-$DATA_MOUNT/etc-kubesolo/cloud-init.yaml}"
+if [ -f "$CLOUDINIT_FILE" ]; then
+    log "Cloud-init found: $CLOUDINIT_FILE"
+    # Phase 1: simple parsing — extract network stanza
+    # TODO: Replace with proper cloud-init parser (Go binary) in Phase 2
+    log_warn "Cloud-init network parsing not yet implemented — falling back to DHCP"
+fi
+
+# Fallback: DHCP on first non-loopback interface
+log "Configuring network via DHCP"
+
+# Bring up loopback
+ip link set lo up
+ip addr add 127.0.0.1/8 dev lo
+
+# Find first ethernet interface
+ETH_DEV=""
+for iface in /sys/class/net/*; do
+    iface="$(basename "$iface")"
+    case "$iface" in
+        lo|docker*|veth*|br*|cni*) continue ;;
+    esac
+    ETH_DEV="$iface"
+    break
+done
+
+if [ -z "$ETH_DEV" ]; then
+    log_err "No network interface found"
+    return 1
+fi
+
+log "Using interface: $ETH_DEV"
+ip link set "$ETH_DEV" up
+
+# Run DHCP client (BusyBox udhcpc)
+if command -v udhcpc >/dev/null 2>&1; then
+    udhcpc -i "$ETH_DEV" -s /usr/share/udhcpc/default.script \
+        -t 10 -T 3 -A 5 -b -q 2>/dev/null || {
+        log_err "DHCP failed on $ETH_DEV"
+        return 1
+    }
+elif command -v dhcpcd >/dev/null 2>&1; then
+    dhcpcd "$ETH_DEV" || {
+        log_err "DHCP failed on $ETH_DEV"
+        return 1
+    }
+else
+    log_err "No DHCP client available (need udhcpc or dhcpcd)"
+    return 1
+fi
+
+log_ok "Network configured on $ETH_DEV"