[feat] persist dynamic tools in session rollout file (#10130)

Add dynamic tools to rollout file for persistence & read from rollout on
resume. Ran a real example and spotted the following in the rollout
file:
```
{"timestamp":"2026-01-29T01:27:57.468Z","type":"session_meta","payload":{"id":"019c075d-3f0b-77e3-894e-c1c159b04b1e","timestamp":"2026-01-29T01:27:57.451Z","...."dynamic_tools":[{"name":"demo_tool","description":"Demo dynamic tool","inputSchema":{"additionalProperties":false,"properties":{"city":{"type":"string"}},"required":["city"],"type":"object"}}],"git":{"commit_hash":"ebc573f15c01b8af158e060cfedd401f043e9dfa","branch":"dev/cc/dynamic-tools","repository_url":"https://github.com/openai/codex.git"}}}
```

codex-rs/core/src/rollout/metadata.rs

@@ -303,6 +303,7 @@ mod tests {
             source: SessionSource::default(),
             model_provider: Some("openai".to_string()),
             base_instructions: None,
+            dynamic_tools: None,
         };
         let session_meta_line = SessionMetaLine {
             meta: session_meta,