Add an experimental Alpine image flow

Stage a complete Alpine x86_64 image stack so \	--image alpineworks like the existing manual Void path instead of relying on Debian-oriented image builds.\n\nAdd make targets plus kernel/rootfs/register helpers that download pinned Alpine artifacts, extract a Firecracker-compatible vmlinux, build a matching mkinitfs initramfs, seed OpenRC services, and register/promote a managed image named alpine.\n\nFold in the bring-up fixes discovered during boot validation: use rootfstype=ext4 in shared boot args, install libgcc/libstdc++ for the opencode binary, and give opencode more time to become ready on cold boots.\n\nValidate with go test ./..., the Alpine helper builds, image promotion, and banger vm create --image alpine --name alp --nat plus guest service and port checks.

internal/imagepreset/preset.go

@@ -43,6 +43,31 @@ var voidBase = []string{
 	"wget",
 }
 
+var alpineBase = []string{
+	"alpine-base",
+	"bash",
+	"ca-certificates",
+	"curl",
+	"docker",
+	"docker-cli-compose",
+	"e2fsprogs",
+	"git",
+	"iproute2",
+	"less",
+	"libgcc",
+	"libstdc++",
+	"make",
+	"mkinitfs",
+	"openssh",
+	"procps-ng",
+	"shadow",
+	"sudo",
+	"tmux",
+	"tree",
+	"vim",
+	"wget",
+}
+
 func DebianBasePackages() []string {
 	return append([]string(nil), debianBase...)
 }
@@ -51,6 +76,10 @@ func VoidBasePackages() []string {
 	return append([]string(nil), voidBase...)
 }
 
+func AlpineBasePackages() []string {
+	return append([]string(nil), alpineBase...)
+}
+
 func Hash(lines []string) string {
 	sum := sha256.Sum256([]byte(strings.Join(lines, "\n") + "\n"))
 	return fmt.Sprintf("%x", sum)