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>

cloud-init/examples/airgapped.yaml

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+# KubeSolo OS Cloud-Init — Air-Gapped Deployment
+# For environments with no internet access.
+# All container images must be pre-loaded into containerd.
+#
+# Place at: /mnt/data/etc-kubesolo/cloud-init.yaml
+
+hostname: airgap-node-01
+
+network:
+  mode: static
+  interface: eth0
+  address: 10.0.0.50/24
+  gateway: 10.0.0.1
+  dns:
+    - 10.0.0.1
+
+kubesolo:
+  local-storage: true
+  # Disable components that need internet
+  extra-flags: "--disable traefik --disable servicelb"
+
+# Pre-loaded images (Phase 2+: auto-import at boot)
+# Images must be placed as tar files on the data partition at:
+#   /mnt/data/images/*.tar
+# They will be imported into containerd on first boot.
+airgap:
+  import-images: true
+  images-dir: /mnt/data/images
+  # registry-mirror: ""  # Optional: local registry mirror

cloud-init/examples/dhcp.yaml

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+# KubeSolo OS Cloud-Init — DHCP Configuration (Default)
+# Place at: /mnt/data/etc-kubesolo/cloud-init.yaml (on data partition)
+# Or pass via boot param: kubesolo.cloudinit=/path/to/this.yaml
+
+hostname: kubesolo-node
+
+network:
+  mode: dhcp
+  # interface: eth0    # Optional: specify interface (auto-detected if omitted)
+  # dns:               # Optional: override DHCP-provided DNS
+  #   - 8.8.8.8
+  #   - 1.1.1.1
+
+kubesolo:
+  # extra-flags: ""    # Additional flags for KubeSolo binary
+  # local-storage: true
+  # apiserver-extra-sans:
+  #   - kubesolo.local

cloud-init/examples/portainer-edge.yaml

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+# KubeSolo OS Cloud-Init — Portainer Edge Agent Integration
+# This config connects the KubeSolo node to a Portainer Business instance
+# via the Edge Agent for remote management.
+#
+# Place at: /mnt/data/etc-kubesolo/cloud-init.yaml
+
+hostname: edge-node-01
+
+network:
+  mode: dhcp
+
+kubesolo:
+  local-storage: true
+  # extra-flags: ""
+
+# Portainer Edge Agent configuration
+# After KubeSolo starts, deploy the Edge Agent as a workload
+portainer:
+  edge-agent:
+    enabled: true
+    # Get these values from Portainer → Environments → Add Environment → Edge Agent
+    edge-id: "your-edge-id-here"
+    edge-key: "your-edge-key-here"
+    portainer-url: "https://portainer.example.com"
+    # Optional: specify Edge Agent version
+    # image: portainer/agent:latest

cloud-init/examples/static-ip.yaml

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+# KubeSolo OS Cloud-Init — Static IP Configuration
+# Place at: /mnt/data/etc-kubesolo/cloud-init.yaml
+
+hostname: kubesolo-edge-01
+
+network:
+  mode: static
+  interface: eth0
+  address: 192.168.1.100/24
+  gateway: 192.168.1.1
+  dns:
+    - 8.8.8.8
+    - 8.8.4.4
+
+kubesolo:
+  extra-flags: "--apiserver-extra-sans kubesolo-edge-01.local"
+  local-storage: true