[kagent / Gemini] Structured output publishes answer as set_model_response call instead of final answer

## Observed symptom [BUG] Structured output: with the Gemini provider, the answer is published as a set_model_response call before validation ### 📋 Prerequisites - [X] I have searched the [existing issues](https://github.com/kagent-dev/kagent/issues) to avoid creating a duplicate - [X] By submitting this issue, you agree to follow our [Code of Conduct](https://github.com/kagent-dev/kagent/blob/main/CODE_OF_CONDUCT.md) - [X] I am using the latest version of the software - [ ] I have tried to clear cache/cookies or used incognito mode (if ui-related) - [X] I can consistently reproduce this issue ### 🎯 Affected Service(s) Not Sure ### 🚦 Impact/Severity Minor inconvenience ### 🐛 Bug Description With a Gemini model on the `Gemini` provider, a structured output answer is published before kagent validates it, so an answer that fai ## Literal error text ``` answer published as set_model_response ``` ## Environment GitHub issue kagent-dev/kagent #3009 ## Trigger / context ### 📋 Prerequisites - [X] I have searched the [existing issues](https://github.com/kagent-dev/kagent/issues) to avoid creating a duplicate - [X] By submitting this issue, you agree to follow our [Code of Conduct](https://github.com/kagent-dev/kagent/blob/main/CODE_OF_CONDUCT.md) - [X] I am using the latest version of the software - [ ] I have tried to clear cache/cookies or used incognito mode (if ui-related) - [X] I can consistently reproduce this issue ### 🎯 Affected Service(s) Not Sure ### 🚦 Impact/Severity Minor inconvenience ### 🐛 Bug Description With a Gemini model on the `Gemini` provider, a structured output answer is published before kagent validates it, so an answer that fails validation still reaches the client. [docs/architecture/structured-output.md](https://github.com/kagent-dev/kagent/blob/e451630265e590a6408c3dea37ee6e38cfa8666b/docs/architecture/structured-output.md) says it should not: > Invalid model output is not published or included in errors because it may contain sensitive data. The path, in the Go ADK runtime at main e4516302: 1. For Gemini, kagent sets only ADK's typed `OutputSchema`, since [`usesRawOutputSchema`](https://github.com/kagent-dev/ka ## Source evidence - https://github.com/kagent-dev/kagent/issues/3009 (2026-09-29T22:05:54Z) — #3009 ## Freshness - classification: FRESH_7D - retrieved_at: 2026-10-02T09:46:06.809152Z - scout_id: C9375ba5fa2 ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome.