fix(v1): use typed ACP turn in Prime Agent harness

[hallerite]

Summary

• update the Prime Agent harness to consume the ACPTurn type exported by the merged ACP base
• restore built-in harness discovery after stacked PR feat(v1): add Prime Agent ACP harness #2440 was restacked onto PRs feat(v1): type ACP prompt results #2438 and feat(v1): integrate nano-RLM training over ACP #2439

Root cause

PR #2440 retained the earlier ACPTurnResult name while PR #2438 landed the public type as ACPTurn. Importing the built-in harness package therefore raised ImportError.

Validation

• exact deterministic V1 CI command: 71 passed
• full test suite exits successfully; credential-gated live tests skipped locally
• uv run ty check verifiers
• uv run ruff check --fix .
• changed-file pre-commit hooks

The branch is based on newest main after RLM hotfix #2442.

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Note

Low Risk
Rename-only type alignment with no logic changes; fixes import/discovery breakage.

Overview
Aligns the Prime Agent harness with the v1 ACP base after the public turn type was renamed from ACPTurnResult to ACPTurn.

The import and acp_turn_result parameter type are updated only; lifecycle handling is unchanged. This removes the ImportError that broke built-in harness package discovery when stacked PRs landed the new name in verifiers.v1.acp but Prime Agent still imported the old symbol.

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