fix(client): anchored default-graph writes for inbox + scope index

Inbox deposits and the per-(account,scope) index append were written into an
explicit GRAPH <plainNuri> named graph, which the real broker stores separately
from the repo's default graph (repo_graph_name with overlay suffix) — so an
anchored default-graph read (read-model.readDoc) never saw them and deposits
did not round-trip. Drop the GRAPH wrapper: the anchor scopes the write to the
repo's default graph, matching the read. Mocks updated accordingly.

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

packages/client/src/store-registry.ts

@@ -422,9 +422,12 @@ export async function createEntityDoc(username: string, scope: Scope): Promise<N
   try {
     await sparqlUpdate(
       s.sessionId,
-      // indexDoc is a NURI in IRI position → assertNuri; entityNuri is a NURI
-      // stored as a literal → escapeLiteral.
-      `INSERT DATA { GRAPH <${assertNuri(indexDoc)}> { <${INDEX_SUBJECT}> <${P.contains}> "${escapeLiteral(entityNuri)}" } }`,
+      // NO explicit `GRAPH <…>` wrapper: the real broker stores each repo's
+      // triples under repo_graph_name(repo_id, overlay_id), not the plain NURI,
+      // so an INSERT into `GRAPH <plainNuri>` targets a phantom graph and does
+      // NOT round-trip. Write the anchored DEFAULT graph instead (the `indexDoc`
+      // anchor scopes it). entityNuri is a NURI stored as a literal → escapeLiteral.
+      `INSERT DATA { <${INDEX_SUBJECT}> <${P.contains}> "${escapeLiteral(entityNuri)}" }`,
       indexDoc,
     );
   } catch (error) {
@@ -440,7 +443,9 @@ async function readScopeIndex(indexDoc: Nuri): Promise<Nuri[]> {
   try {
     const res = await sparqlQuery(
       s.sessionId,
-      `SELECT ?e WHERE { GRAPH <${assertNuri(indexDoc)}> { <${INDEX_SUBJECT}> <${P.contains}> ?e } }`,
+      // NO explicit `GRAPH <…>` clause — read the anchored DEFAULT graph (see
+      // the note in createEntityDoc). The `indexDoc` anchor scopes the query.
+      `SELECT ?e WHERE { <${INDEX_SUBJECT}> <${P.contains}> ?e }`,
       undefined,
       indexDoc,
     );