fix(duckdb): allow opening non-existent database files

crates/dbx-core/src/db/duckdb_driver.rs

@@ -39,7 +39,13 @@ fn validate_duckdb_path(path: &str) -> Result<(), String> {
         return Err(format!("Database file path is a directory, not a file: {}", path));
     }
     if !path_obj.exists() {
-        return Err(format!("Database file does not exist: {}", path));
+        // DuckDB creates a new database file on open when the parent directory
+        // exists. Only reject paths whose parent directory is missing.
+        if let Some(parent) = path_obj.parent() {
+            if !parent.as_os_str().is_empty() && !parent.exists() {
+                return Err(format!("Parent directory does not exist: {}", parent.display()));
+            }
+        }
     }
     Ok(())
 }