docs: "what is emulated (and how it goes away)" recap table + read-path reconcile

README: new section with a recap table (11 rows) — for each emulated behavior:
what the consumer sees (SDK-shaped API), how it's emulated on one shared wallet,
the real NextGraph target, and the lib-only migration. Makes "emulated ≠ real,
migration is a lib-only swap" explicit.
simulation.md: opening banner that EVERYTHING in the file is emulation pending
real NextGraph; corrected the stale read-path paragraph (per-doc anchored, never
an anchorless union-scan). read-model.md: reactivity bullet aligned to per-doc.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/read-model.md

@@ -95,7 +95,8 @@ There is **no reactive union query**. So reactivity is assembled:
 
 - keep a lightweight reactive subscription — `doc_subscribe`, or the ORM on an
   **already-opened single store** (never a per-entity fan-out) — on the synced docs;
-- on its change signal, **re-run** the one-shot union `sparql_query`.
+- on its change signal, **re-run** the bounded set of per-doc anchored
+  `sparql_query`s (`readModel.readUnion`) — never an anchorless union-scan.
 
 Keep the reactive ORM strictly to already-opened single stores; it is a change
 *signal* source here, not the list source.