refactor: remove backward compat wrapper and legacy snapshot support

- Remove PurgeSnapshots wrapper; callers use PurgeSnapshotsWithOptions directly
- Update snapshot create --prune to call PurgeSnapshotsWithOptions
- Remove TestSnapshotPurgeOptions (tested Go struct assignment, no value)
- Remove legacy no-name snapshot tests (TestPurgeKeepLatest_LegacyNoNameSnapshots,
  TestPurgeKeepLatest_MixedNamedAndLegacy)
- Remove legacy format test cases from TestParseSnapshotName
- Update parseSnapshotName doc to not mention legacy format

internal/vaultik/helpers.go

@@ -80,8 +80,9 @@ func parseSnapshotTimestamp(snapshotID string) (time.Time, error) {
 }
 
 // parseSnapshotName extracts the snapshot name from a snapshot ID.
-// Format: hostname_snapshotname_timestamp (3 parts) or hostname_timestamp (2 parts, no name).
-// Returns the snapshot name, or empty string if no name component is present.
+// Format: hostname_snapshotname_timestamp — the middle part(s) between hostname
+// and the RFC3339 timestamp are the snapshot name (may contain underscores).
+// Returns the snapshot name, or empty string if the ID is malformed.
 func parseSnapshotName(snapshotID string) string {
 	parts := strings.Split(snapshotID, "_")
 	if len(parts) < 3 {

internal/vaultik/helpers_test.go

@@ -20,26 +20,11 @@ func TestParseSnapshotName(t *testing.T) {
 			snapshotID: "server1_system_2026-02-15T09:30:00Z",
 			want:       "system",
 		},
-		{
-			name:       "no snapshot name (legacy format)",
-			snapshotID: "myhost_2026-01-12T14:41:15Z",
-			want:       "",
-		},
 		{
 			name:       "name with underscores",
 			snapshotID: "myhost_my_special_backup_2026-03-01T00:00:00Z",
 			want:       "my_special_backup",
 		},
-		{
-			name:       "single part (edge case)",
-			snapshotID: "nounderscore",
-			want:       "",
-		},
-		{
-			name:       "empty string",
-			snapshotID: "",
-			want:       "",
-		},
 	}
 
 	for _, tt := range tests {
@@ -89,31 +74,3 @@ func TestParseSnapshotTimestamp(t *testing.T) {
 		})
 	}
 }
-
-func TestSnapshotPurgeOptions(t *testing.T) {
-	opts := &SnapshotPurgeOptions{
-		KeepLatest: true,
-		Name:       "home",
-		Force:      true,
-	}
-	if !opts.KeepLatest {
-		t.Error("Expected KeepLatest to be true")
-	}
-	if opts.Name != "home" {
-		t.Errorf("Expected Name to be 'home', got %q", opts.Name)
-	}
-	if !opts.Force {
-		t.Error("Expected Force to be true")
-	}
-
-	opts2 := &SnapshotPurgeOptions{
-		OlderThan: "30d",
-		Name:      "system",
-	}
-	if opts2.OlderThan != "30d" {
-		t.Errorf("Expected OlderThan to be '30d', got %q", opts2.OlderThan)
-	}
-	if opts2.Name != "system" {
-		t.Errorf("Expected Name to be 'system', got %q", opts2.Name)
-	}
-}

internal/vaultik/purge_per_name_test.go

@@ -228,53 +228,6 @@ func TestPurgeOlderThan_WithNameFilter(t *testing.T) {
 	assert.Contains(t, remaining, "testhost_home_2026-01-01T00:00:00Z")
 }
 
-func TestPurgeKeepLatest_LegacyNoNameSnapshots(t *testing.T) {
-	// Legacy snapshots without a name component (hostname_timestamp).
-	// Should be grouped together under empty-name.
-	snapshotIDs := []string{
-		"testhost_2026-01-01T00:00:00Z",
-		"testhost_2026-01-01T01:00:00Z",
-		"testhost_2026-01-01T02:00:00Z",
-	}
-
-	v := setupPurgeTest(t, snapshotIDs)
-
-	err := v.PurgeSnapshotsWithOptions(&vaultik.SnapshotPurgeOptions{
-		KeepLatest: true,
-		Force:      true,
-	})
-	require.NoError(t, err)
-
-	remaining := listRemainingSnapshots(t, v)
-	assert.Len(t, remaining, 1)
-	assert.Contains(t, remaining, "testhost_2026-01-01T02:00:00Z")
-}
-
-func TestPurgeKeepLatest_MixedNamedAndLegacy(t *testing.T) {
-	// Mix of named snapshots and legacy ones (no name).
-	snapshotIDs := []string{
-		"testhost_2026-01-01T00:00:00Z",
-		"testhost_home_2026-01-01T01:00:00Z",
-		"testhost_2026-01-01T02:00:00Z",
-		"testhost_home_2026-01-01T03:00:00Z",
-	}
-
-	v := setupPurgeTest(t, snapshotIDs)
-
-	err := v.PurgeSnapshotsWithOptions(&vaultik.SnapshotPurgeOptions{
-		KeepLatest: true,
-		Force:      true,
-	})
-	require.NoError(t, err)
-
-	remaining := listRemainingSnapshots(t, v)
-
-	// Should keep latest of each group: latest legacy + latest home
-	assert.Len(t, remaining, 2)
-	assert.Contains(t, remaining, "testhost_2026-01-01T02:00:00Z")
-	assert.Contains(t, remaining, "testhost_home_2026-01-01T03:00:00Z")
-}
-
 func TestPurgeKeepLatest_ThreeNames(t *testing.T) {
 	// Three different snapshot names with multiple snapshots each.
 	snapshotIDs := []string{

internal/vaultik/snapshot.go

@@ -95,7 +95,10 @@ func (v *Vaultik) CreateSnapshot(opts *SnapshotCreateOptions) error {
 		log.Info("Pruning enabled - deleting old snapshots and unreferenced blobs")
 		v.printlnStdout("\nPruning old snapshots (keeping latest)...")
 
-		if err := v.PurgeSnapshots(true, "", true); err != nil {
+		if err := v.PurgeSnapshotsWithOptions(&SnapshotPurgeOptions{
+			KeepLatest: true,
+			Force:      true,
+		}); err != nil {
 			return fmt.Errorf("prune: purging old snapshots: %w", err)
 		}
 
@@ -528,18 +531,7 @@ type SnapshotPurgeOptions struct {
 	Name       string // Filter purge to a specific snapshot name
 }
 
-// PurgeSnapshots removes old snapshots based on criteria.
-// When keepLatest is true, retention is applied per snapshot name — the latest
-// snapshot for each distinct name is kept.
-func (v *Vaultik) PurgeSnapshots(keepLatest bool, olderThan string, force bool) error {
-	return v.PurgeSnapshotsWithOptions(&SnapshotPurgeOptions{
-		KeepLatest: keepLatest,
-		OlderThan:  olderThan,
-		Force:      force,
-	})
-}
-
-// PurgeSnapshotsWithOptions removes old snapshots based on criteria with full options.
+// PurgeSnapshotsWithOptions removes old snapshots based on criteria.
 // When KeepLatest is true, retention is applied per snapshot name — the latest
 // snapshot for each distinct name is kept. If Name is non-empty, only snapshots
 // matching that name are considered for purge.