docs: #875 follow-up — repo surfaces + reproduction URLs + CHANGELOG

Remaining in-repo surfaces carrying the same retracted or broken
claims as the public pages fixed in the previous two commits.

CONTRIBUTING.md
 - "Palace structure matters ... 34% retrieval improvement" → reframed
   as scoping (same rewording applied to the website equivalents).

benchmarks/BENCHMARKS.md
 - Add a prominent "Important caveat" block at the top of the
   "Comparison vs Published Systems" table explaining that R@5
   (retrieval recall) and QA accuracy are different metrics, with
   citations to Mastra, Mem0, and Supermemory's own published
   methodology pages. Annotate the specific competitor rows whose
   numbers are QA accuracy, not retrieval recall.
 - Annotate the `hybrid v4 + rerank 100%` row to note that the 99.4
   → 100 step was tuned on 3 specific wrong answers (already disclosed
   further down in the doc under "Benchmark Integrity"); the honest
   hybrid figure is held-out 98.4%.
 - Fix the broken clone URL — `aya-thekeeper/mempal` no longer points
   at anything; now `MemPalace/mempalace`.

benchmarks/README.md + benchmarks/HYBRID_MODE.md
 - Same clone-URL fix applied.

CHANGELOG.md
 - Add a ### Documentation entry under [Unreleased] v3.3.0 that names
   #875 and summarises the scope of the rewrite.

CHANGELOG.md

@@ -41,6 +41,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 - Add `docs/CLOSETS.md` — closet layer overview
 - Fix stale `milla-jovovich/*` org URLs in website and plugin manifests (#787)
 - Fix remaining stale org URLs in contributor docs (#808)
+- Rewrite `README.md` and `mempalaceofficial.com` benchmark pages to remove category-error cross-system comparisons (R@5 retrieval recall had been listed next to competitor QA accuracy under one column), remove the retracted "+34% palace boost" claim from the surfaces where it had remained, replace the `100%` Haiku-rerank headline with the honest held-out `98.4%` R@5, drop the LoCoMo `100%` top-50 row (retrieval-bypass artefact), and fix the broken `aya-thekeeper/mempal` reproduction URL (#875)
+- Add `docs/HISTORY.md` as the canonical home for corrections, retractions, and public notices; move the 2026-04-07 "Note from Milla & Ben" and the 2026-04-11 impostor-domain notice out of `README.md`
+- Add v3.3.0 reproduction result JSONLs and the deterministic `seed=42` 50/450 LongMemEval split under `benchmarks/` — every BENCHMARKS.md claim reproduces exactly
 
 ### Internal
 - Add test coverage for `mine_lock`, closets, entity metadata, BM25, and diary