XY-849: [ELF benchmark suite] Add operator debugging UX cases

[yvette-carlisle]

Summary

• Add the operator_debugging_ux real-world job suite with five fixtures covering dropped evidence, rerank promotion, provider latency/failure, rebuild result changes, and misleading relation context.
• Extend the benchmark runner and reports with operator-debug evidence, trace/viewer links, raw SQL avoidance, dropped-candidate visibility, trace completeness, and repair clarity scoring.
• Add read-only viewer support for direct trace_id links and document the operator UX report.

Validation

• cargo make real-world-job-operator-ux
• cargo make real-world-job-smoke
• cargo test -p elf-eval --test real_world_job_benchmark
• cargo test -p elf-api admin_viewer_is_admin_prefixed_and_read_only
• cargo make fmt
• cargo make lint-fix
• cargo make checks
• Semantic drift audit: pass