Default `GOOSE_SUBAGENT_MAX_TURNS` leads to subagent failures

The default `GOOSE_SUBAGENT_MAX_TURNS` is only 25, which is both highly limiting for research tasks that require a lot of turns searching the web, but also appears to be surprising to the parent agent. My parent agent (Qwen3.8-Flash-Next) kept `peek`ing the subagents and seeing the same results and concluded they must be stuck or looping so decided to kill them and give up on them. I guess `peek` needs to show the "I've run out of turns, tell me to keep going" error, but really it just seems like `GOOSE_SUBAGENT_MAX_TURNS` should be bumped substantially by default.

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**Please provide the following information**
- **OS & Arch:** Linux
- **Interface:** ACP
- **Version:** 2b9cd967e94cde85f73042c1198333f7ba511a42
- **Extensions enabled:** defaults, i think
- **Provider & Model:** Qwen3.8-Flash-Next locally

Trouvez la définition de la constante GOOSE_SUBAGENT_MAX_TURNS dans la base de code, probablement dans un fichier de configuration ou de constantes. Comprenez comment l’agent parent utilise 'peek' pour vérifier l’état du sous-agent. Augmentez la valeur par défaut et vérifiez que la modification ne casse pas les tests existants. Vérifiez si la fonctionnalité 'peek' doit être mise à jour pour communiquer correctement l’état de la limite de tours.

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