Add ty type checker to CI and fix type errors (fixes bug from PR #157) (#192)

* 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.

* Fix remaining ty type errors

- Fix slack_mcp_reader.py channel parameter can be None
- Fix embedding_compute.py ContextProp type issue
- Fix searcher_base.py method override signatures
- Fix chunking_utils.py chunk_text assignment
- Fix slack_rag.py and twitter_rag.py return types
- Fix email.py and image_rag.py method overrides

* Fix multimodal benchmark scripts type errors

- Fix undefined LeannRetriever -> LeannMultiVector
- Add proper type casts for HuggingFace Dataset iteration
- Cast task config values to correct types
- Add type annotations for dataset row dicts

* Enable ty check for multimodal scripts in CI

All type errors in multimodal scripts have been fixed, so we can now
include them in the CI type checking.

* Fix all test type errors and enable ty check on tests

- Fix test_basic.py: search() takes str not list
- Fix test_cli_prompt_template.py: add type: ignore for Mock assignments
- Fix test_prompt_template_persistence.py: match BaseSearcher.search signature
- Fix test_prompt_template_e2e.py: add type narrowing asserts after skip
- Fix test_readme_examples.py: use explicit kwargs instead of **model_args
- Fix metadata_filter.py: allow Optional[MetadataFilters]
- Update CI to run ty check on tests

* Format code with ruff

* Format searcher_base.py

tests/test_readme_examples.py

@@ -97,17 +97,17 @@ def test_backend_options():
 
     with tempfile.TemporaryDirectory() as temp_dir:
         # Use smaller model in CI to avoid memory issues
-        if os.environ.get("CI") == "true":
-            model_args = {
-                "embedding_model": "sentence-transformers/all-MiniLM-L6-v2",
-                "dimensions": 384,
-            }
-        else:
-            model_args = {}
+        is_ci = os.environ.get("CI") == "true"
+        embedding_model = (
+            "sentence-transformers/all-MiniLM-L6-v2" if is_ci else "facebook/contriever"
+        )
+        dimensions = 384 if is_ci else None
 
         # Test HNSW backend (as shown in README)
         hnsw_path = str(Path(temp_dir) / "test_hnsw.leann")
-        builder_hnsw = LeannBuilder(backend_name="hnsw", **model_args)
+        builder_hnsw = LeannBuilder(
+            backend_name="hnsw", embedding_model=embedding_model, dimensions=dimensions
+        )
         builder_hnsw.add_text("Test document for HNSW backend")
         builder_hnsw.build_index(hnsw_path)
         assert Path(hnsw_path).parent.exists()
@@ -115,7 +115,9 @@ def test_backend_options():
 
         # Test DiskANN backend (mentioned as available option)
         diskann_path = str(Path(temp_dir) / "test_diskann.leann")
-        builder_diskann = LeannBuilder(backend_name="diskann", **model_args)
+        builder_diskann = LeannBuilder(
+            backend_name="diskann", embedding_model=embedding_model, dimensions=dimensions
+        )
         builder_diskann.add_text("Test document for DiskANN backend")
         builder_diskann.build_index(diskann_path)
         assert Path(diskann_path).parent.exists()