Remove runtime-bundle image dependencies

Hard-cut banger away from source-checkout runtime bundles as an implicit source of\nimage and host defaults. Managed images now own their full boot set,\nimage build starts from an existing registered image, and daemon startup\nno longer synthesizes a default image from host paths.\n\nResolve Firecracker from PATH or firecracker_bin, make SSH keys config-owned\nwith an auto-managed XDG default, replace the external name generator and\npackage manifests with Go code, and keep the vsock helper as a companion\nbinary instead of a user-managed runtime asset.\n\nUpdate the manual scripts, web/CLI forms, config surface, and docs around\nthe new build/manual flow and explicit image registration semantics.\n\nValidation: GOCACHE=/tmp/banger-gocache go test ./..., bash -n scripts/*.sh,\nand make build.

internal/model/types.go

@@ -35,15 +35,10 @@ const (
 )
 
 type DaemonConfig struct {
-	RuntimeDir          string
 	LogLevel            string
 	WebListenAddr       string
 	FirecrackerBin      string
 	SSHKeyPath          string
-	NamegenPath         string
-	CustomizeScript     string
-	VSockAgentPath      string
-	DefaultWorkSeed     string
 	AutoStopStaleAfter  time.Duration
 	StatsPollInterval   time.Duration
 	MetricsPollInterval time.Duration
@@ -53,12 +48,6 @@ type DaemonConfig struct {
 	TapPoolSize         int
 	DefaultDNS          string
 	DefaultImageName    string
-	DefaultRootfs       string
-	DefaultBaseRootfs   string
-	DefaultKernel       string
-	DefaultInitrd       string
-	DefaultModulesDir   string
-	DefaultPackagesFile string
 }
 
 type Image struct {
@@ -71,7 +60,6 @@ type Image struct {
 	KernelPath                    string    `json:"kernel_path"`
 	InitrdPath                    string    `json:"initrd_path,omitempty"`
 	ModulesDir                    string    `json:"modules_dir,omitempty"`
-	PackagesPath                  string    `json:"packages_path,omitempty"`
 	BuildSize                     string    `json:"build_size,omitempty"`
 	SeededSSHPublicKeyFingerprint string    `json:"seeded_ssh_public_key_fingerprint,omitempty"`
 	Docker                        bool      `json:"docker"`
@@ -152,7 +140,7 @@ type VMSetRequest struct {
 
 type ImageBuildRequest struct {
 	Name       string
-	BaseRootfs string
+	FromImage  string
 	Size       string
 	KernelPath string
 	InitrdPath string