fix: invert FindAndOpenSQLiteStore existence check

The condition was backwards — it exited with "database already exists"
when the file was found, and tried to open it when it did not exist.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/service/node_service_impl.go

@@ -118,10 +118,7 @@ func (s *nodeServiceImpl) getPermContext() (*permContext, error) {
 		}
 		for relType, pLevel := range permRelLevels {
 			for _, tgt := range node.Relations[string(relType)] {
-				eff := curr.level
-				if pLevel < eff {
-					eff = pLevel
-				}
+				eff := min(curr.level, pLevel)
 				if eff > pc.levels[tgt] {
 					queue = append(queue, entry{tgt, eff})
 				}

src/store/graph_store_sqlite.go

@@ -60,7 +60,7 @@ func InitSQLiteStore(path string) error {
 
 // FindAndOpenSQLiteStore opens the SQLite database. If the AX_DB_PATH environment
 // variable is set, it uses that path directly. Otherwise, it walks up from the
-// current working directory to find an .ax.db file.
+// current working directory to find an .ax/ax.db file.
 func FindAndOpenSQLiteStore() (GraphStore, error) {
 	if dbpath := os.Getenv("AX_DB_PATH"); dbpath != "" {
 		return NewSQLiteStore(dbpath)
@@ -68,13 +68,11 @@ func FindAndOpenSQLiteStore() (GraphStore, error) {
 
 	dataRoot, err := FindDataRoot(".local", "share")
 	if err != nil {
-		fmt.Fprintln(os.Stderr, "failed to find data dir:", err)
-		os.Exit(1)
+		return nil, fmt.Errorf("failed to find data dir: %w", err)
 	}
 	dbPath := filepath.Join(dataRoot, "ax.db")
-	if _, err := os.Stat(dbPath); err == nil {
-		fmt.Fprintln(os.Stderr, "database already exists:", dbPath)
-		os.Exit(1)
+	if _, err := os.Stat(dbPath); err != nil {
+		return nil, fmt.Errorf("no database found at %s: run 'ax init' first", dbPath)
 	}
 	return NewSQLiteStore(dbPath)
 }