🐛 Fix sync from zero

internal/store/sync_store.go

@@ -36,8 +36,9 @@ type SyncChange struct {
 }
 
 // Pull returns all sync_log rows with version > sinceVersion.
-// It calls Prune first with a 30-day TTL.
-// If the client is behind a prune marker it returns ErrSyncStale.
+// It calls Prune first with a 30-day TTL. A zero-version pull is a bootstrap
+// and may proceed past the prune marker; non-zero clients behind the marker
+// must perform a full re-sync.
 func (s *SyncStore) Pull(ctx context.Context, sinceVersion int64) ([]SyncChange, int64, error) {
 	if err := s.Prune(ctx, 30*24*time.Hour); err != nil {
 		return nil, 0, err
@@ -58,9 +59,11 @@ func (s *SyncStore) Pull(ctx context.Context, sinceVersion int64) ([]SyncChange,
 		if err := rows.Scan(&c.Entity, &c.EntityID, &c.Op, &c.Version, &c.Payload); err != nil {
 			return nil, 0, err
 		}
-		// First row with entity="_pruned" means client is stale.
 		if c.Entity == pruneEntity {
-			return nil, 0, ErrSyncStale
+			if sinceVersion != 0 {
+				return nil, 0, ErrSyncStale
+			}
+			continue
 		}
 		if c.Version > maxVersion {
 			maxVersion = c.Version

internal/store/sync_store_test.go

@@ -76,8 +76,8 @@ func TestSyncPruneStaleClient(t *testing.T) {
 		t.Fatalf("Prune: %v", err)
 	}
 
-	// A stale client (since=0) should get ErrSyncStale.
-	_, _, err := s.Pull(ctx, 0)
+	// A client with an existing sync position behind the marker is stale.
+	_, _, err := s.Pull(ctx, 1)
 	if !errors.Is(err, store.ErrSyncStale) {
 		t.Fatalf("expected ErrSyncStale, got %v", err)
 	}