XY-954: [ELF benchmark P1] Add scheduled memory task scoring and trace gate

[yvette-carlisle]

Summary

• Add a scheduled_memory real-world benchmark suite with fixture-backed task readback, freshness/currentness, action rationale, execution trace, and source-mutation guards.
• Add cargo make tasks and durable scheduled-memory Markdown/JSON benchmark reports.
• Update aggregate benchmark/docs/ledger evidence to 60 jobs across 16 suites with 53 pass and 7 blocked, while preserving hosted/private scheduler non-claim boundaries.

Validation

• cargo make fmt
• cargo make lint-fix
• cargo make checks
• cargo make real-world-memory-scheduled
• cargo make real-world-memory
• cargo test -p elf-eval --test real_world_job_benchmark -- --test-threads=1
• jq empty docs/research/2026-06-11-competitor-strength-adoption-report.json docs/research/2026-06-16-dreaming-readiness-stage-ledger.json docs/research/2026-06-16-scheduled-memory-task-scoring-report.json apps/elf-eval/fixtures/real_world_memory/scheduled_memory/*.json