#1442 Feature request: support chat title generating from Xcode's agent

Description

Currently, whenever I start a new chat in Xcode, the title is always just a quote from my prompt. Is there a way to change that? I understand this isn't a priority feature by any means though. 🥲

Total noob here so this report was mostly written by Claude...:

**Environment**
- Strata v0.1.40.2 (git clone), Windows, RTX 3090
- Client: Xcode agent (Codex-style, via `/v1/responses`) on a Mac, connecting over LAN
- Model: [qwen3.8-flash-next-iq3_s]

**What I'm seeing**
Xcode's agent conversation list never shows generated titles. Every conversation is titled with the start of my first prompt, truncated with "…". Agent chats otherwise work fine.

**What the log shows**
After the first agent turn, Strata receives a second, much smaller request (~8.5k prompt tokens vs ~28k for the normal agent turns) that finishes after ~140 tokens. It is preceded by this warning:

```
[strata] response_format json_schema: the Python package jsonschema is not installed, so answers are only checked to be one JSON object (python -m pip install "jsonschema>=4.23,<5")
```

I suspect this is Xcode's title-generation request. The request seems to succeed, but Xcode doesn't use the result, which makes me think the returned JSON doesn't match the schema Xcode sent.

[After installing jsonschema: describe whether titles started working, or whether nothing changed.]

**Feature requests**
1. **Debug logging for request/response bodies.** An option (flag or env var) to log the incoming `response_format` schema and the returned JSON for `/v1/responses` requests. Right now there's no way to see why a client rejects a response that Strata considers successful.
2. **Enforce json_schema, not just "one JSON object".** If feasible, use constrained decoding or retry/validation so the output actually conforms to the requested schema, with or without the optional package.
3. **Make `jsonschema` a normal dependency** (or have the installer/UPDATE.bat check for it), so the warning doesn't show up on a fresh setup.

Happy to test changes or share more logs.

Thanks again for this amazing project. Truly god sent.