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/20-persistent-mount.sh

@@ -0,0 +1,47 @@
+#!/bin/sh
+# 20-persistent-mount.sh — Mount persistent data partition and bind-mount writable paths
+
+if [ "$KUBESOLO_NOPERSIST" = "1" ]; then
+    log "Running in RAM-only mode — no persistent storage"
+    # Create tmpfs-backed directories so KubeSolo has somewhere to write
+    mkdir -p /var/lib/kubesolo /var/lib/containerd /etc/kubesolo /var/log /usr/local
+    return 0
+fi
+
+# Wait for device to appear (USB, slow disks, virtio)
+log "Waiting for data device: $KUBESOLO_DATA_DEV"
+WAIT_SECS=30
+for i in $(seq 1 "$WAIT_SECS"); do
+    [ -b "$KUBESOLO_DATA_DEV" ] && break
+    sleep 1
+done
+
+if [ ! -b "$KUBESOLO_DATA_DEV" ]; then
+    log_err "Data device $KUBESOLO_DATA_DEV not found after ${WAIT_SECS}s"
+    return 1
+fi
+
+# Mount data partition
+mkdir -p "$DATA_MOUNT"
+mount -t ext4 -o noatime "$KUBESOLO_DATA_DEV" "$DATA_MOUNT" || {
+    log_err "Failed to mount $KUBESOLO_DATA_DEV"
+    return 1
+}
+log_ok "Mounted $KUBESOLO_DATA_DEV at $DATA_MOUNT"
+
+# Create persistent directory structure (first boot)
+for dir in kubesolo containerd etc-kubesolo log usr-local network; do
+    mkdir -p "$DATA_MOUNT/$dir"
+done
+
+# Ensure target mount points exist
+mkdir -p /var/lib/kubesolo /var/lib/containerd /etc/kubesolo /var/log /usr/local
+
+# Bind mount persistent paths
+mount --bind "$DATA_MOUNT/kubesolo"     /var/lib/kubesolo
+mount --bind "$DATA_MOUNT/containerd"   /var/lib/containerd
+mount --bind "$DATA_MOUNT/etc-kubesolo" /etc/kubesolo
+mount --bind "$DATA_MOUNT/log"          /var/log
+mount --bind "$DATA_MOUNT/usr-local"    /usr/local
+
+log_ok "Persistent bind mounts configured"