Add Go daemon-driven VM control plane

Replace the shell-only user workflow with `banger` and `bangerd`: Cobra commands, XDG/SQLite-backed state, managed VM and image lifecycle, and a Bubble Tea TUI for browsing and operating VMs.\n\nKeep Firecracker orchestration behind the daemon so VM specs become persistent objects, and add repo entrypoints for building, installing, and documenting the new flow while still delegating rootfs customization to the existing shell tooling.\n\nHarden the control plane around real usage by reclaiming Firecracker API sockets for the user, restarting stale daemons after rebuilds, and returning the correct `vm.create` payload so the CLI and TUI creation flow work reliably.\n\nValidation: `go test ./...`, `make build`, and a host-side smoke test with `./banger vm create --name codex-smoke`.

internal/daemon/images.go

@@ -0,0 +1,131 @@
+package daemon
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"banger/internal/api"
+	"banger/internal/model"
+)
+
+func (d *Daemon) BuildImage(ctx context.Context, params api.ImageBuildParams) (model.Image, error) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	name := params.Name
+	if name == "" {
+		name = fmt.Sprintf("image-%d", model.Now().Unix())
+	}
+	if _, err := d.FindImage(ctx, name); err == nil {
+		return model.Image{}, fmt.Errorf("image name already exists: %s", name)
+	}
+	if d.config.RepoRoot == "" {
+		return model.Image{}, fmt.Errorf("repo root not found; set repo_root in config.toml")
+	}
+	baseRootfs := params.BaseRootfs
+	if baseRootfs == "" {
+		baseRootfs = d.config.DefaultBaseRootfs
+	}
+	if baseRootfs == "" {
+		return model.Image{}, fmt.Errorf("base rootfs is required")
+	}
+	id, err := model.NewID()
+	if err != nil {
+		return model.Image{}, err
+	}
+	now := model.Now()
+	artifactDir := filepath.Join(d.layout.ImagesDir, id)
+	if err := os.MkdirAll(artifactDir, 0o755); err != nil {
+		return model.Image{}, err
+	}
+	rootfsPath := filepath.Join(artifactDir, "rootfs.ext4")
+	script := filepath.Join(d.config.RepoRoot, "customize.sh")
+	if _, err := os.Stat(script); err != nil {
+		return model.Image{}, fmt.Errorf("customize.sh not found at %s", script)
+	}
+	args := []string{script, baseRootfs, "--out", rootfsPath}
+	if params.Size != "" {
+		args = append(args, "--size", params.Size)
+	}
+	kernelPath := params.KernelPath
+	if kernelPath == "" {
+		kernelPath = d.config.DefaultKernel
+	}
+	if kernelPath != "" {
+		args = append(args, "--kernel", kernelPath)
+	}
+	initrdPath := params.InitrdPath
+	if initrdPath == "" {
+		initrdPath = d.config.DefaultInitrd
+	}
+	if initrdPath != "" {
+		args = append(args, "--initrd", initrdPath)
+	}
+	modulesDir := params.ModulesDir
+	if modulesDir == "" {
+		modulesDir = d.config.DefaultModulesDir
+	}
+	if modulesDir != "" {
+		args = append(args, "--modules", modulesDir)
+	}
+	if params.Docker {
+		args = append(args, "--docker")
+	}
+	cmd := exec.CommandContext(ctx, "bash", args...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	cmd.Stdin = os.Stdin
+	cmd.Dir = d.config.RepoRoot
+	if err := cmd.Run(); err != nil {
+		_ = os.RemoveAll(artifactDir)
+		return model.Image{}, err
+	}
+	image := model.Image{
+		ID:           id,
+		Name:         name,
+		Managed:      true,
+		ArtifactDir:  artifactDir,
+		RootfsPath:   rootfsPath,
+		KernelPath:   kernelPath,
+		InitrdPath:   initrdPath,
+		ModulesDir:   modulesDir,
+		PackagesPath: d.config.DefaultPackagesFile,
+		BuildSize:    params.Size,
+		Docker:       params.Docker,
+		CreatedAt:    now,
+		UpdatedAt:    now,
+	}
+	if err := d.store.UpsertImage(ctx, image); err != nil {
+		return model.Image{}, err
+	}
+	return image, nil
+}
+
+func (d *Daemon) DeleteImage(ctx context.Context, idOrName string) (model.Image, error) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	image, err := d.FindImage(ctx, idOrName)
+	if err != nil {
+		return model.Image{}, err
+	}
+	vms, err := d.store.FindVMsUsingImage(ctx, image.ID)
+	if err != nil {
+		return model.Image{}, err
+	}
+	if len(vms) > 0 {
+		return model.Image{}, fmt.Errorf("image %s is still referenced by %d VM(s)", image.Name, len(vms))
+	}
+	if err := d.store.DeleteImage(ctx, image.ID); err != nil {
+		return model.Image{}, err
+	}
+	if image.Managed && image.ArtifactDir != "" {
+		if err := os.RemoveAll(image.ArtifactDir); err != nil {
+			return model.Image{}, err
+		}
+	}
+	return image, nil
+}