docs: reconcile arXiv benchmark figures after post-fix review

[cdeust]

Closes #347

What changed

• Align the README LoCoMo headline with the canonical post-fix run: Recall@10 94.35%, MRR 0.8279, n=1,986, code SHA 2f45bcb.
• Add a supersession warning to the pre-fix results document.
• Resolve the provenance of the historical 0.794 / 0.926 comparator and label it explicitly as noncanonical.
• Align the current LongMemEval headline on the clean July run: Recall@10 98.2%, MRR 0.9167, n=500, code SHA 28145f0; retain 98.4% / 0.9124 only as the named historical E1 v3 ablation snapshot.
• Label BEAM 0.591 as a five-conversation, n=100 retrieval-proxy MRR at code SHA a071d89 and remove the invalid comparison with the paper end-to-end metric.
• Align the thermodynamic and context-assembly arXiv sources and all publication-facing appendices, then regenerate both PDFs.
• Add a versioned audit of the arXiv-facing figures and their sources.

Opus 5 review follow-up

Resolved the residual stale 92.6% in the Popper appendix, the LongMemEval 98.4 / 98.2 / 97.8 split, and the missing BEAM metric/protocol audit identified in the issue review.

Why

The public documents mixed current post-fix results with historical or protocol-specific measurements. This made the arXiv draft ambiguous and, for BEAM, risked comparing incommensurable retrieval-proxy and end-to-end metrics.

Validation

• scripts/check_doc_claims.py
• git diff --check
• Relative Markdown-link validation for all changed Markdown files
• Exact artifact/provenance assertions for LoCoMo and LongMemEval
• Exact 14-row LoCoMo table parity across the post-fix result, Markdown paper, and LaTeX paper
• Clean LaTeX builds for both papers, with no undefined citations or references
• PDF text extraction confirming 98.2%, 94.35%, and 0.591 with their metric framing