Add comprehensive documentation and templates for LangChain skill development

- Introduced a new reference document for streaming output issues, detailing the differences between streaming APIs and providing solutions for common problems.
- Created a structured output issues reference, outlining the use of `with_structured_output`, `response_format`, and schema enforcement strategies.
- Added a user query convention guide to standardize structured questions for skill authors, including block types for queries and data gathering.
- Implemented a template for a chat model, encapsulating API key management, request payload construction, and response handling.
- Established a symlink for the LangChain dev guide in the Claude skills directory for easier access.
- Initialized a skills lock file to manage dependencies and versions for the LangChain dev guide.

.agents/skills/langchain-dev-guide/reference/cn-models/integration-tests.md

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+# Chat Model Integration Tests
+
+After writing `chat_model.py`, you must write integration tests to verify the model class works correctly.
+
+## Test Framework
+
+Use `ChatModelIntegrationTests` from `langchain_tests` as the base class, and run tests with pytest.
+
+Install dependencies:
+
+```bash
+pip install langchain-tests pytest python-dotenv
+```
+
+## Test File Structure
+
+Place test files following standard unit test directory conventions:
+
+```
+src/<models_dir>/<model_name>/
+├── __init__.py
+├── chat_model.py
+└── ...
+
+tests/
+└── test_chat_<model_name>.py
+```
+
+## Standard Test Class
+
+For a new provider (e.g., Qwen, GLM), create a test class that inherits from `ChatModelIntegrationTests` and provides the following properties:
+
+```python
+from __future__ import annotations
+
+import pytest
+from dotenv import load_dotenv
+from langchain_core.language_models import BaseChatModel
+from langchain_tests.integration_tests import ChatModelIntegrationTests
+
+from models.qwen.chat_model import ChatQwen  # replace with the actual import path
+
+load_dotenv()
+
+
+class TestChatQwen(ChatModelIntegrationTests):
+    @property
+    def chat_model_class(self) -> type[BaseChatModel]:
+        return ChatQwen
+
+    @property
+    def chat_model_params(self) -> dict:
+        return {
+            "model": "qwen-plus",
+            "temperature": 0,
+        }
+```
+
+### Required Properties
+
+| Property | Description |
+|----------|-------------|
+| `chat_model_class` | Returns the chat model class under test. |
+| `chat_model_params` | Parameters for creating an instance. Must include `model`; `temperature: 0` is recommended for deterministic results. |
+
+## Running Tests
+
+```bash
+# Run tests for a single model
+pytest tests/test_chat_<model_name>.py -v
+
+# Skip tests marked as xfail (run only expected passes)
+pytest tests/test_chat_<model_name>.py -v -m "not xfail"
+
+# Run all model tests
+pytest tests/ -v
+```
+
+## Common Issues
+
+After setting up the test, you will likely encounter the following issues. Address them before concluding tests pass.
+
+### Model package not importable
+
+By default, the `<models_dir>/` directory is not installed as a Python package, so `from <models_dir>.xxx import ...` in tests will fail. Two changes are needed in `pyproject.toml`:
+
+**1) Add build-system config:**
+
+```toml
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["<models_dir>"]
+```
+
+**2) Install in editable mode:**
+
+```bash
+uv pip install -e .
+```
+
+Without this, pytest fails with `ModuleNotFoundError: No module named '<models_dir>'`.
+
+### Async tests not running (pytest-asyncio strict mode)
+
+pytest-asyncio defaults to `Mode.STRICT`, which requires every async test to have an `@pytest.mark.asyncio` decorator. `langchain_tests` async methods lack this decorator.
+
+Add to `pyproject.toml`:
+
+```toml
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+```
+
+Without this, all async tests (`test_ainvoke`, `test_astream`, `test_abatch`, etc.) fail with "async def functions are not natively supported."