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/twitter_rag.py

@@ -11,6 +11,7 @@ Usage:
 
 import argparse
 import asyncio
+from typing import Any
 
 from apps.base_rag_example import BaseRAGExample
 from apps.twitter_data.twitter_mcp_reader import TwitterMCPReader
@@ -116,7 +117,7 @@ class TwitterMCPRAG(BaseRAGExample):
             print("5. Try running the MCP server command directly to test it")
             return False
 
-    async def load_data(self, args) -> list[str]:
+    async def load_data(self, args) -> list[dict[str, Any]]:
         """Load Twitter bookmarks via MCP server."""
         print(f"Connecting to Twitter MCP server: {args.mcp_server}")