host api alignment (#7)

* feat: add Firecracker API client methods for VM pause/resume and snapshots

Add PatchVm, GetVm, PutSnapshotCreate, and PutSnapshotLoad methods to the
API client, along with supporting types (VmState, SnapshotCreateParams,
SnapshotLoadParams, MemBackend).

* feat: add snapshot data layer - contract types, model, store, config

Add SnapshotID and snapshot contract types, SnapshotRecord model,
store interface CRUD methods with file store implementation,
snapshot paths helper, SnapshotsDir config, and directory creation.

* feat: add runtime methods for VM pause, resume, snapshot, and restore

Implement Pause, Resume, CreateSnapshot, and RestoreBoot on the
firecracker Runtime. RestoreBoot launches a jailer, stages snapshot
files into the chroot, loads the snapshot, and resumes the VM.

* feat: add daemon snapshot create, restore, and reconciliation logic

Implement CreateSnapshot (pause, snapshot, COW-copy disk, resume),
RestoreSnapshot (COW-copy disk, RestoreBoot, wait for guest),
GetSnapshot, ListSnapshots, DeleteSnapshotByID, and crash recovery
reconciliation for snapshot and restore operations.

* feat: add HTTP endpoints for snapshot create, get, list, delete, restore

Wire 5 snapshot routes: POST /machines/{id}/snapshots (create),
GET /machines/{id}/snapshots (list), GET /snapshots/{id} (get),
DELETE /snapshots/{id} (delete), POST /snapshots/{id}/restore (restore).

* fix: cross-device rename, restore network, and snapshot cleanup

- Replace os.Rename with copy+remove for moving snapshot files out of
  /proc/<pid>/root/ (cross-device link error on Linux)
- Reconfigure network interface after snapshot load so the restored VM
  uses its own tap device instead of the source VM's
- Clean partial snapshot dirs immediately on failure instead of only
  via reconcile
- Reject snapshot requests while a machine operation is already pending

* fix: test and modify snapshot runtime

* feat: snapshot lifecycle update, align runtime issues between host image
and daemon

internal/store/file_store.go

@@ -23,9 +23,10 @@ type persistedOperations struct {
 }
 
 type persistedState struct {
-	Artifacts []model.ArtifactRecord `json:"artifacts"`
-	Machines  []model.MachineRecord  `json:"machines"`
-	Volumes   []model.VolumeRecord   `json:"volumes"`
+	Artifacts []model.ArtifactRecord  `json:"artifacts"`
+	Machines  []model.MachineRecord   `json:"machines"`
+	Volumes   []model.VolumeRecord    `json:"volumes"`
+	Snapshots []model.SnapshotRecord  `json:"snapshots"`
 }
 
 func NewFileStore(statePath string, operationsPath string) (*FileStore, error) {
@@ -274,6 +275,73 @@ func (s *FileStore) DeleteOperation(_ context.Context, machineID contracthost.Ma
 	})
 }
 
+func (s *FileStore) CreateSnapshot(_ context.Context, record model.SnapshotRecord) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	return s.updateState(func(state *persistedState) error {
+		for _, snap := range state.Snapshots {
+			if snap.ID == record.ID {
+				return fmt.Errorf("store: snapshot %q already exists", record.ID)
+			}
+		}
+		state.Snapshots = append(state.Snapshots, record)
+		return nil
+	})
+}
+
+func (s *FileStore) GetSnapshot(_ context.Context, id contracthost.SnapshotID) (*model.SnapshotRecord, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	state, err := s.readState()
+	if err != nil {
+		return nil, err
+	}
+	for i := range state.Snapshots {
+		if state.Snapshots[i].ID == id {
+			record := state.Snapshots[i]
+			return &record, nil
+		}
+	}
+	return nil, ErrNotFound
+}
+
+func (s *FileStore) ListSnapshotsByMachine(_ context.Context, machineID contracthost.MachineID) ([]model.SnapshotRecord, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	state, err := s.readState()
+	if err != nil {
+		return nil, err
+	}
+	var result []model.SnapshotRecord
+	for _, snap := range state.Snapshots {
+		if snap.MachineID == machineID {
+			result = append(result, snap)
+		}
+	}
+	if result == nil {
+		result = []model.SnapshotRecord{}
+	}
+	return result, nil
+}
+
+func (s *FileStore) DeleteSnapshot(_ context.Context, id contracthost.SnapshotID) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	return s.updateState(func(state *persistedState) error {
+		for i := range state.Snapshots {
+			if state.Snapshots[i].ID == id {
+				state.Snapshots = append(state.Snapshots[:i], state.Snapshots[i+1:]...)
+				return nil
+			}
+		}
+		return ErrNotFound
+	})
+}
+
 func (s *FileStore) readOperations() (*persistedOperations, error) {
 	var operations persistedOperations
 	if err := readJSONFile(s.operationsPath, &operations); err != nil {
@@ -387,6 +455,7 @@ func emptyPersistedState() persistedState {
 		Artifacts: []model.ArtifactRecord{},
 		Machines:  []model.MachineRecord{},
 		Volumes:   []model.VolumeRecord{},
+		Snapshots: []model.SnapshotRecord{},
 	}
 }
 
@@ -404,6 +473,9 @@ func normalizeState(state *persistedState) {
 	if state.Volumes == nil {
 		state.Volumes = []model.VolumeRecord{}
 	}
+	if state.Snapshots == nil {
+		state.Snapshots = []model.SnapshotRecord{}
+	}
 }
 
 func normalizeOperations(operations *persistedOperations) {