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/code_rag.py

@@ -6,6 +6,7 @@ optimized chunking parameters.
 
 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))
@@ -77,7 +78,7 @@ class CodeRAG(BaseRAGExample):
             help="Try to preserve import statements in chunks (default: True)",
         )
 
-    async def load_data(self, args) -> list[str]:
+    async def load_data(self, args) -> list[dict[str, Any]]:
         """Load code files and convert to AST-aware chunks."""
         print(f"🔍 Scanning code repository: {args.repo_dir}")
         print(f"📁 Including extensions: {args.include_extensions}")
@@ -88,14 +89,6 @@ class CodeRAG(BaseRAGExample):
         if not repo_path.exists():
             raise ValueError(f"Repository directory not found: {args.repo_dir}")
 
-        # Load code files with filtering
-        reader_kwargs = {
-            "recursive": True,
-            "encoding": "utf-8",
-            "required_exts": args.include_extensions,
-            "exclude_hidden": True,
-        }
-
         # Create exclusion filter
         def file_filter(file_path: str) -> bool:
             """Filter out unwanted files and directories."""
@@ -120,8 +113,11 @@ class CodeRAG(BaseRAGExample):
             # Load documents with file filtering
             documents = SimpleDirectoryReader(
                 args.repo_dir,
-                file_extractor=None,  # Use default extractors
-                **reader_kwargs,
+                file_extractor=None,
+                recursive=True,
+                encoding="utf-8",
+                required_exts=args.include_extensions,
+                exclude_hidden=True,
             ).load_data(show_progress=True)
 
             # Apply custom filtering