Add ty type checker to CI and fix type errors

- Add ty (Astral's fast Python type checker) to GitHub CI workflow
- Fix type annotations across all RAG apps:
  - Update load_data return types from list[str] to list[dict[str, Any]]
  - Fix base_rag_example.py to properly handle dict format from create_text_chunks
- Fix type errors in leann-core:
  - chunking_utils.py: Add explicit type annotations
  - cli.py: Fix return type annotations for PDF extraction functions
  - interactive_utils.py: Fix readline import type handling
- Fix type errors in apps:
  - wechat_history.py: Fix return type annotations
  - document_rag.py, code_rag.py: Replace **kwargs with explicit arguments
- Add ty configuration to pyproject.toml

This resolves the bug introduced in PR #157 where create_text_chunks()
changed to return list[dict] but callers were not updated.

apps/image_rag.py

@@ -14,6 +14,7 @@ import argparse
 import pickle
 import tempfile
 from pathlib import Path
+from typing import Any
 
 import numpy as np
 from PIL import Image
@@ -65,7 +66,7 @@ class ImageRAG(BaseRAGExample):
             help="Batch size for CLIP embedding generation (default: 32)",
         )
 
-    async def load_data(self, args) -> list[str]:
+    async def load_data(self, args) -> list[dict[str, Any]]:
         """Load images, generate CLIP embeddings, and return text descriptions."""
         self._image_data = self._load_images_and_embeddings(args)
         return [entry["text"] for entry in self._image_data]