Merge fix/tool-result-markdown-rendering into main

## Goal
Merge `fix/tool-result-markdown-rendering` into `main` after syncing `main` with upstream.

## Commands
```bash
git checkout main
git merge fix/tool-result-markdown-rendering
uv run python -m pytest
git push origin main
```

## Acceptance Criteria
- Feature branch changes in `main`
- Tests pass after merge
