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/config/config.go

@@ -0,0 +1,125 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"time"
+
+	toml "github.com/pelletier/go-toml"
+
+	"banger/internal/model"
+	"banger/internal/paths"
+)
+
+type fileConfig struct {
+	RepoRoot           string `toml:"repo_root"`
+	DefaultImageName   string `toml:"default_image_name"`
+	DefaultBaseRootfs  string `toml:"default_base_rootfs"`
+	DefaultKernel      string `toml:"default_kernel"`
+	DefaultInitrd      string `toml:"default_initrd"`
+	DefaultModulesDir  string `toml:"default_modules_dir"`
+	DefaultPackages    string `toml:"default_packages_file"`
+	AutoStopStaleAfter string `toml:"auto_stop_stale_after"`
+	StatsPollInterval  string `toml:"stats_poll_interval"`
+	MetricsPoll        string `toml:"metrics_poll_interval"`
+	BridgeName         string `toml:"bridge_name"`
+	BridgeIP           string `toml:"bridge_ip"`
+	CIDR               string `toml:"cidr"`
+	DefaultDNS         string `toml:"default_dns"`
+}
+
+func Load(layout paths.Layout) (model.DaemonConfig, error) {
+	cfg := model.DaemonConfig{
+		RepoRoot:            paths.DetectRepoRoot(),
+		AutoStopStaleAfter:  0,
+		StatsPollInterval:   model.DefaultStatsPollInterval,
+		MetricsPollInterval: model.DefaultMetricsPollInterval,
+		BridgeName:          model.DefaultBridgeName,
+		BridgeIP:            model.DefaultBridgeIP,
+		CIDR:                model.DefaultCIDR,
+		DefaultDNS:          model.DefaultDNS,
+		DefaultImageName:    "default",
+	}
+	if cfg.RepoRoot != "" {
+		cfg.DefaultBaseRootfs = filepath.Join(cfg.RepoRoot, "rootfs.ext4")
+		cfg.DefaultKernel = filepath.Join(cfg.RepoRoot, "wtf/root/boot/vmlinux-6.8.0-94-generic")
+		cfg.DefaultInitrd = filepath.Join(cfg.RepoRoot, "wtf/root/boot/initrd.img-6.8.0-94-generic")
+		cfg.DefaultModulesDir = filepath.Join(cfg.RepoRoot, "wtf/root/lib/modules/6.8.0-94-generic")
+		cfg.DefaultPackagesFile = filepath.Join(cfg.RepoRoot, "packages.apt")
+	}
+
+	path := filepath.Join(layout.ConfigDir, "config.toml")
+	info, err := os.Stat(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return cfg, nil
+		}
+		return cfg, err
+	}
+	if info.IsDir() {
+		return cfg, nil
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return cfg, err
+	}
+	var file fileConfig
+	if err := toml.Unmarshal(data, &file); err != nil {
+		return cfg, err
+	}
+	if file.RepoRoot != "" {
+		cfg.RepoRoot = file.RepoRoot
+	}
+	if file.DefaultImageName != "" {
+		cfg.DefaultImageName = file.DefaultImageName
+	}
+	if file.DefaultBaseRootfs != "" {
+		cfg.DefaultBaseRootfs = file.DefaultBaseRootfs
+	}
+	if file.DefaultKernel != "" {
+		cfg.DefaultKernel = file.DefaultKernel
+	}
+	if file.DefaultInitrd != "" {
+		cfg.DefaultInitrd = file.DefaultInitrd
+	}
+	if file.DefaultModulesDir != "" {
+		cfg.DefaultModulesDir = file.DefaultModulesDir
+	}
+	if file.DefaultPackages != "" {
+		cfg.DefaultPackagesFile = file.DefaultPackages
+	}
+	if file.BridgeName != "" {
+		cfg.BridgeName = file.BridgeName
+	}
+	if file.BridgeIP != "" {
+		cfg.BridgeIP = file.BridgeIP
+	}
+	if file.CIDR != "" {
+		cfg.CIDR = file.CIDR
+	}
+	if file.DefaultDNS != "" {
+		cfg.DefaultDNS = file.DefaultDNS
+	}
+	if file.AutoStopStaleAfter != "" {
+		duration, err := time.ParseDuration(file.AutoStopStaleAfter)
+		if err != nil {
+			return cfg, err
+		}
+		cfg.AutoStopStaleAfter = duration
+	}
+	if file.StatsPollInterval != "" {
+		duration, err := time.ParseDuration(file.StatsPollInterval)
+		if err != nil {
+			return cfg, err
+		}
+		cfg.StatsPollInterval = duration
+	}
+	if file.MetricsPoll != "" {
+		duration, err := time.ParseDuration(file.MetricsPoll)
+		if err != nil {
+			return cfg, err
+		}
+		cfg.MetricsPollInterval = duration
+	}
+	return cfg, nil
+}