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/claude_rag.py

@@ -5,6 +5,7 @@ Supports Claude export data from JSON files.
 
 import sys
 from pathlib import Path
+from typing import Any
 
 # Add parent directory to path for imports
 sys.path.insert(0, str(Path(__file__).parent))
@@ -80,7 +81,7 @@ class ClaudeRAG(BaseRAGExample):
 
         return export_files
 
-    async def load_data(self, args) -> list[str]:
+    async def load_data(self, args) -> list[dict[str, Any]]:
         """Load Claude export data and convert to text chunks."""
         export_path = Path(args.export_path)