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/00-early-mount.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+# 00-early-mount.sh — Mount essential virtual filesystems
+
+mount -t proc proc /proc 2>/dev/null || true
+mount -t sysfs sysfs /sys 2>/dev/null || true
+mount -t devtmpfs devtmpfs /dev 2>/dev/null || true
+mount -t tmpfs tmpfs /tmp
+mount -t tmpfs tmpfs /run
+
+mkdir -p /dev/pts /dev/shm
+mount -t devpts devpts /dev/pts
+mount -t tmpfs tmpfs /dev/shm
+
+# Mount cgroup2 unified hierarchy
+mkdir -p /sys/fs/cgroup
+mount -t cgroup2 cgroup2 /sys/fs/cgroup 2>/dev/null || {
+    log_warn "cgroup v2 mount failed; attempting v1 fallback"
+    mount -t tmpfs cgroup /sys/fs/cgroup
+    for subsys in cpu cpuacct memory devices freezer pids; do
+        mkdir -p "/sys/fs/cgroup/$subsys"
+        mount -t cgroup -o "$subsys" "cgroup_${subsys}" "/sys/fs/cgroup/$subsys" 2>/dev/null || true
+    done
+}