[FIX] [BREAKING]: Evaluate probe verdicts over final traces

[Spencer Schoenberg (spencrr)]

Description

Behavioral probes now evaluate the verdict once over the final trace instead of after every response. This fixes sequence and prior-condition probes, which cannot be judged correctly from partial prefixes. Probes no longer stop on a detected verdict by default; pass stop_when when an online condition should end the trace early.

Final verdict evidence is stored on Result.final_trace_evaluation, online stop evidence stays on turns with EvaluationPurpose.STOP_CHECK, and Result.trace_end_reason records why the trace ended. Final evaluation runs while the session is still active.

Because probe status semantics change, the private xdist envelope moves to rampart.xdist.v3. Controllers reject v2 worker payloads instead of mixing per-turn and final-trace statuses. The trace-contract declaration records a compatible change against main: fingerprinted files change only by removing the list-based resolve_as_probe helper and updating docstrings.

Depends on #148.

Breaking changes

• Probe verdicts are computed once over the final trace. Single-prompt probes with deterministic evaluators keep their verdicts. Multi-turn probes can resolve differently because the evaluator's scope now applies to the whole trace, which runs up to max_turns unless stop_when is set.
• For multi-turn probes, stochastic evaluators such as LLM judges are sampled once per run instead of once per turn, so trial pass rates can shift.
• Without stop_when, adaptive drivers receive no online evaluator feedback and may run to max_turns.
• resolve_as_probe(eval_results=...) is removed; use resolve_probe_verdict(evaluation=...).
• Controllers and workers must run the same RAMPART version; v2 xdist payloads are rejected.

The upgrade note in docs/probes/behavioral.md covers these changes.

Checklist

• pre-commit run --all-files passes
• Tests added or updated for changes — one-call verdict cadence, sequence and prior-condition probes, temporal scopes, explicit stopping and reuse, driver feedback, budgets, session ordering, summaries, error results, and the v3 xdist envelope
• Documentation updated

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