Feature/custom folder multi vector/ add Readme to LEANN MCP (#189)

* Add custom folder support and improve image loading for multi-vector retrieval

- Enhanced _load_images_from_dir with recursive search support and better error handling
- Added support for WebP format and RGB conversion for all image modes
- Added custom folder CLI arguments (--custom-folder, --recursive, --rebuild-index)
- Improved documentation and removed completed TODO comment

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Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* Format code style in leann_multi_vector.py for better readability

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Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* docs: polish README performance tip section

- Fix typo: 'matrilize' -> 'materialize'
- Improve clarity and formatting of --no-recompute flag explanation
- Add code block for better readability

* format

---------

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

packages/leann-mcp/README.md

@@ -53,6 +53,11 @@ leann build my-project --docs $(git ls-files)
 # Start Claude Code
 claude
 ```
+**Performance tip**: For maximum speed when storage space is not a concern, add the `--no-recompute` flag to your build command. This materializes all tensors and stores them on disk, avoiding recomputation on subsequent builds:
+
+```bash
+leann build my-project --docs $(git ls-files) --no-recompute
+```
 
 ## 🚀 Advanced Usage Examples to build the index