Summarize the conversation without tool output on request - #587

The new commits wire `ToolRendering` and `max_output_tokens` through `ModelSummarizer`, add the `## About the User` and `## Commitments` prompt sections, and test all three. The code matches the description; my only finding is that the description's claim that `Full` output is unchanged "byte for byte" is qualified by testing only the default-rendering path, which is accurate. One gap: the body lists `model_summarizer_tests.rs` coverage but the added tests for markers/max_tokens are described only in the first section, which is sufficient. No reportable defects. _The code index is behind this pull request (indexed at `13a38cd9a17e`), so retrieved context may be out of date._

No findings.