docs+refactor(client): fidelity pass — id identity, drop connections, no faux-login, accurate NextGraph framing

Align the polyfill's surface and docs with the verified NextGraph reality and
remove application-level concepts:

- Identity is an ID, not a username: AccountRecord.id, shim predicate shim:id,
  normalizeId; accounts core becomes IdentityStore (set/clear/get) — the faux
  login/logout framing is gone (identity is set at wallet-import time).
- Relationship/connection is an application concept, not a platform primitive
  (NextGraph has no bilateral-connection primitive: grantee is unpersisted
  scaffolding, cap-send is unimplemented). Remove connections.ts; caps exposes
  only a directed grantRead(doc, granteeId) + a read-only protectedDocsOf(owner).
  Delete the now-dead isolation.ts social-visibility axis.
- Inbox docs: NextGraph has no separate curator — the recipient's own verifier
  unseals and applies each queued sealed message inline (process_inbox);
  inbox_post_link is a proposed/future API. Stop attributing the emulated
  curator to the platform.
- Read isolation reframed around the outcome: no cap -> empty union read;
  targeted read of an unheld repo -> RepoNotFound; cap introspection
  (canRead/governsRead) is emulation-only with no NextGraph API behind it.
- read-model.md corrected: the listing path is per-doc ANCHORED default-graph
  queries, never the anchorless GRAPH ?g union (that is O(wallet)); the probe
  section no longer claims the opposite.
- README recap table restructured (target | current NextGraph status | current
  emulation); INDEX_ACCOUNT documented as reservedAccount("index") in the
  sentinel namespace; de-domained generic-layer comments; softened tone.

Consumer application (Festipod) rewired separately to own the relationship
concept and feed the lib an id. Lib gates: bun test 83 pass / 0 fail, tsc clean.

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

packages/client/test/read-model.test.ts

@@ -34,7 +34,7 @@ function inject(triplesByDoc: Record<string, Array<[string, string]>>) {
   configure({ ng: ng as any, useShape: (() => {}) as any });
   configureStoreRegistry({
     getSession: async () => ({ sessionId: "sid-rm", privateStoreId: "priv" }),
-    normalizeUser: (u: string) => u,
+    normalizeId: (u: string) => u,
   });
   return ng;
 }
@@ -96,7 +96,7 @@ test("a doc that fails to read is skipped, not aborting the batch", async () =>
   configure({ ng: ng as any, useShape: (() => {}) as any });
   configureStoreRegistry({
     getSession: async () => ({ sessionId: "sid-rm", privateStoreId: "priv" }),
-    normalizeUser: (u: string) => u,
+    normalizeId: (u: string) => u,
   });
 
   const subjects = await readUnion(["did:ng:o:ok", "did:ng:o:bad"]);