card refresh: curation and review fixes

README.md

@@ -193,6 +193,31 @@ an existence proof. Demo-grade: no auth, no SLA. Reference:
 curl "https://mcp.openballast.org/lookup?question=Where+was+Douglas+Adams+born%3F&level=5"
 ```
 
+## Curation & processing
+
+This is not a Wikidata mirror — it is a curated, serving-shaped derivation.
+What was done to the dump, in order:
+
+1. **Inclusion.** Every item with a resolvable English label (`mul`
+   honored with English fallback). Wikimedia-internal pages (categories,
+   templates, disambiguation scaffolding) filtered by `instance of`.
+2. **Statement filtering.** External identifiers, media references, and
+   URL datatypes are dropped at publish — they ground nothing a language
+   model can answer with. What remains is the answerable slice:
+   entity-, time-, quantity-, string-, and coordinate-valued statements.
+3. **Ranking.** Each entity scored by a composite of log(sitelinks) +
+   log(claim count) and assigned to 8 nested buckets at fixed population
+   fractions. The rank axis is the product: it turns knowledge-per-byte
+   into a download-time decision, which no raw dump or existing mirror
+   offers.
+4. **Rendering contract.** The published measurements were made against a
+   fixed evidence rendering (the `Facts about X:` block above) over these
+   exact bytes; truncation semantics (entity-outside-level, object-drop)
+   are preserved end-to-end in every distribution format. That
+   measurement anchoring — the corpus is the artifact the numbers were
+   measured on, versioned together — is the second thing a mirror does
+   not give you.
+
 ## Limitations
 
 - **Coverage follows notability.** The rank composite (sitelinks + claim