feat(compact): drop the forced summarize tool_choice after tool results

[mikasenghaas]

Summary

• Drop the forced tool_choice={"function": {"name": "summarize"}} on the compact harness's post-tool-result model call — summarize stays the only advertised tool there and the system prompt still requires saving notes, but the model now has to choose the call itself
• A non-summarize call after a tool result still ends the rollout with no answer, so protocol violations become an observable (and trainable) negative signal instead of being mechanically prevented
• Simplify chat() accordingly (the tool_choice parameter had no other caller)

Verification

16-task wikispeedia eval (eval split, Qwen/Qwen3-4B on a local vLLM), this branch vs the forced protocol:

• Unforced (this PR): 0/16 solved. 15/16 rollouts end at their first tool result by emitting another task tool call (wiki_click_link ×11 + one more later, wiki_go_back ×3) instead of summarize — even with only summarize advertised, the server-side parser extracts the call and the protocol ends the rollout. Exactly one rollout followed the click→summarize loop unforced (7 turns) and then answered wrong. Trace dashboard: https://app.primeintellect.ai/dashboard/evaluations/wk9qajkt4afdnsx95enhgqoo
• Forced (main), same task split, concurrent 500-task run: ~38% solve rate over the first 61 rollouts.

This reproduces the GLM-5.2 finding that motivated the forcing (advertising summarize alone is not enough). As-is, the unforced protocol yields no successful rollouts for Qwen3-4B — fine as a hard negative training signal, unusable for evals. If we want this behavior switchable, a force_summarize: bool = True knob on CompactingHarnessConfig is probably the better shape than removing the forcing outright.

Breaking

• Compact-harness rollouts where the model replies to a tool result with anything other than a summarize call (or a plain-text finish) now end without an answer instead of being steered into summarize. Weaker instruction-followers will score lower under this harness.

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