fix(harness): keep tool-call markup out of summaries and tool-less answers - #277

Reviewed 0 files; 0 findings. 9 files could not be reviewed: crates/tinyagents-harness/src/agent_loop/README.md, crates/tinyagents-harness/src/agent_loop/dialect.rs, crates/tinyagents-harness/src/agent_loop/model_call.rs, crates/tinyagents-harness/src/agent_loop/run_loop.rs, crates/tinyagents-harness/src/agent_loop/run_loop_recovery_tests.rs, crates/tinyagents-harness/src/agent_loop/run_loop_withheld_tests.rs, crates/tinyagents-harness/src/summarization/README.md, crates/tinyagents-harness/src/summarization/model_summarizer.rs, crates/tinyagents-harness/src/summarization/model_summarizer_tests.rs.

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