XY-1073: Add quality scoreboard grammar and adversarial benchmark gates

[yvette-carlisle]

Summary

• Add the P4 quality scoreboard grammar for typed non-pass states, evidence classes, external-adapter manifest boundaries, and unqualified-win claim blocking.
• Add adversarial quality fixtures covering source authority conflicts, stale current answers, unsupported-claim refusal, private excluded spans, and correction persistence.
• Add benchmark/runbook docs for the new quality scoreboard and adversarial gate.

Validation

• cargo make real-world-memory-adversarial-quality
• cargo nextest run -p elf-eval --test real_world_job_benchmark adversarial_quality_fixtures_score_scoreboard_gates adversarial_quality_fixture_catches_unsupported_and_stale_regressions adversarial_quality_repeated_fixture_run_is_deterministic
• cargo nextest run -p elf-eval --test real_world_job_benchmark real_world_memory_fixtures_report_aggregate_metrics
• cargo make checks

Handoff Note

• Decodex produced the original XY-1073 commit but failed before creating a PR; the retained lane entered failed/orphaned handoff state after interrupt.
• Manual recovery amended the generated commit to clarify job-level vs external-adapter typed non-pass scoreboard fields, then reran validation before this PR.