XY-1157: Run independent review and Decodex closeout for final ELF memory system goal

[yvette-carlisle]

Summary

• add the final source-backed project memory closeout evidence for XY-1157
• wire the closeout report into README, benchmarking index, docs log, and report-path tests
• preserve competitor and unsupported-claim boundaries while recording validation and review requirements

Validation

• cargo test -p elf-eval --test real_world_job_benchmark closeout -- --nocapture
• python3 scripts/check-docs.py
• git diff --check 853abc3..HEAD
• cargo make checks
• cargo test -p elf-eval --test real_world_job_benchmark source_backed_quality -- --nocapture
• cargo make source-backed-memory-quality
• decodex status --json
• independent skeptic review: pass, no P0/P1 findings