v0.5.0

## Fixed

- **Multi-turn tool calls on thinking-mode models no longer return HTTP 400.** Every assistant message in the conversation now carries `reasoning_content` when thinking is enabled — not just tool-call rounds — matching DeepSeek's actual API validation, which rejects any assistant message missing the field even though the docs describe non-tool-call reasoning as "ignored".
- **Final-pass wire-payload sanitizer** in the chat-completions client forces a non-empty `reasoning_content` placeholder onto any assistant message still missing one at request time. This is the last line of defense after engine-side and build-side substitution, so sessions restored from older checkpoints, sub-agents that append messages directly, and cached prefix mismatches all produce a valid request.
- On a `reasoning_content`-related 400, the client now logs the offending message indices to make future regressions diagnosable.
- Stripped phantom `web.run` references from prompts and the `web_search` tool surface (#25).

## Changed

- Header / UI widget refactor in the TUI (internal cleanup, no user-visible behavior change).

## Install

```bash
npm install -g deepseek-tui
```

Or from source:
```bash
git clone https://github.com/Hmbown/DeepSeek-TUI.git
cd DeepSeek-TUI
cargo install --path crates/tui --locked   # requires Rust 1.85+
```

Full changelog: https://github.com/Hmbown/DeepSeek-TUI/blob/main/CHANGELOG.md