feat: show MCP tool calls in TUI (#836)

Adds logic for the `McpToolCallBegin` and `McpToolCallEnd` events in
`codex-rs/tui/src/chatwidget.rs` so they get entries in the conversation
history in the TUI.

Building on top of https://github.com/openai/codex/pull/829, here is the
result of running:

```
cargo run --bin codex -- 'what is the weather in san francisco tomorrow'
```


![image](https://github.com/user-attachments/assets/db4a79bb-4988-46cb-acb2-446d5ba9e058)

codex-rs/tui/Cargo.toml

@@ -18,10 +18,12 @@ codex-ansi-escape = { path = "../ansi-escape" }
 codex-core = { path = "../core", features = ["cli"] }
 color-eyre = "0.6.3"
 crossterm = "0.28.1"
+mcp-types = { path = "../mcp-types" }
 ratatui = { version = "0.29.0", features = [
     "unstable-widget-ref",
     "unstable-rendered-line-info",
 ] }
+serde_json = "1"
 shlex = "1.3.0"
 tokio = { version = "1", features = [
     "io-std",