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

tests/test_cli_prompt_template.py

@@ -123,7 +123,7 @@ class TestPromptTemplateStoredInEmbeddingOptions:
         cli = LeannCLI()
 
         # Mock load_documents to return a document so builder is created
-        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])
+        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])  # type: ignore[assignment]
 
         parser = cli.create_parser()
 
@@ -175,7 +175,7 @@ class TestPromptTemplateStoredInEmbeddingOptions:
         cli = LeannCLI()
 
         # Mock load_documents to return a document so builder is created
-        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])
+        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])  # type: ignore[assignment]
 
         parser = cli.create_parser()
 
@@ -230,7 +230,7 @@ class TestPromptTemplateStoredInEmbeddingOptions:
         cli = LeannCLI()
 
         # Mock load_documents to return a document so builder is created
-        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])
+        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])  # type: ignore[assignment]
 
         parser = cli.create_parser()
 
@@ -307,7 +307,7 @@ class TestPromptTemplateStoredInEmbeddingOptions:
         cli = LeannCLI()
 
         # Mock load_documents to return a document so builder is created
-        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])
+        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])  # type: ignore[assignment]
 
         parser = cli.create_parser()
 
@@ -376,7 +376,7 @@ class TestPromptTemplateStoredInEmbeddingOptions:
         cli = LeannCLI()
 
         # Mock load_documents to return a document so builder is created
-        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])
+        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])  # type: ignore[assignment]
 
         parser = cli.create_parser()
 
@@ -432,7 +432,7 @@ class TestPromptTemplateFlowsToComputeEmbeddings:
         cli = LeannCLI()
 
         # Mock load_documents to return a simple document
-        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])
+        cli.load_documents = Mock(return_value=[{"text": "test content", "metadata": {}}])  # type: ignore[assignment]
 
         parser = cli.create_parser()