XY-865: [ELF benchmark vNext P1] Publish real-world comparison report and adoption plan

[yvette-carlisle]

Summary

• Add the June 10 post-P1 real-world comparison report with exact benchmark commands, run ids, typed outcomes, remaining gaps, and adoption implications.
• Update README benchmark claims and the benchmarking index to separate fixture-backed ELF evidence from live-baseline-only external adapter evidence.
• Refresh the external-adapter manifest and test expectation for the current post-P1 outcome counts.

Validation

• cargo make real-world-memory
• cargo make real-world-memory-project-decisions
• cargo make real-world-memory-production-ops
• cargo make real-world-memory-evolution
• cargo make real-world-job-operator-ux
• semantic_drift_audit.py --repo . --json
• cargo make fmt
• cargo make lint-fix
• cargo make checks
• git diff --check

Notes

Private-corpus and credentialed provider checks were not run because the required operator-owned inputs were not supplied. The report keeps those states as typed blocked boundaries instead of benchmark passes.