Update README to reflect VECTOR type

Author: BohuTANG

README.md

@@ -14,7 +14,7 @@ uv run databend-aiserver --port 8815
 | Function | Signature | Purpose | Output |
 | :--- | :--- | :--- | :--- |
 | **ai_list_files** | `(stage_location, max_files)` | List objects in a stage for inspection/sampling. | Table with file details (`path`, `size`, etc.) |
-| **ai_embed_1024** | `(text)` | Generate 1024-dim embeddings (default: Qwen). | `ARRAY(FLOAT NULL)` |
+| **ai_embed_1024** | `(text)` | Generate 1024-dim embeddings (default: Qwen). | `VECTOR(1024)` |
 | **ai_parse_document** | `(stage_location, path)` | Parse docs (PDF, DOCX, Images, etc.) to Markdown. | `VARIANT` (pages, metadata) |
 
 ## Usage
@@ -27,7 +27,7 @@ RETURNS TABLE (stage_name VARCHAR, relative_path VARCHAR, path VARCHAR, is_dir B
 LANGUAGE PYTHON HANDLER = 'ai_list_files' ADDRESS = '<your-ai-server-address>';
 
 CREATE OR REPLACE FUNCTION ai_embed_1024(VARCHAR)
-RETURNS ARRAY(FLOAT NULL)
+RETURNS VECTOR(1024)
 LANGUAGE PYTHON HANDLER = 'ai_embed_1024' ADDRESS = '<your-ai-server-address>';
 
 CREATE OR REPLACE FUNCTION ai_parse_document(stage_location STAGE_LOCATION, path VARCHAR)