## Summary
Fixes an issue where `thinking` content blocks in Claude Code responses
were not being parsed, resulting in empty `AssistantMessage` content
arrays.
## Changes
- Added `ThinkingBlock` dataclass to handle thinking content with
`thinking` and `signature` fields
- Updated client parsing logic in `_internal/client.py` to recognize and
create `ThinkingBlock` instances
- Added comprehensive test coverage for thinking block functionality
## Before
```python
# Claude Code response with thinking block resulted in:
AssistantMessage(content=[]) # Empty content!
```
## After
```python
# Now correctly parses to:
AssistantMessage(content=[
ThinkingBlock(thinking="...", signature="...")
])
```
Fixes#27
---------
Co-authored-by: Dickson Tsai <dickson@anthropic.com>
