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/caps.test.ts

@@ -13,7 +13,7 @@ test("protected documents: owner + explicitly granted principals only", () => {
   caps.open("did:ng:o:prot", "protected", "alice");
   expect(caps.canRead("did:ng:o:prot", "alice")).toBe(true);
   expect(caps.canRead("did:ng:o:prot", "bob")).toBe(false);
-  caps.grantRead("did:ng:o:prot", "bob"); // bob becomes a connection of alice
+  caps.grantRead("did:ng:o:prot", "bob"); // a directed grant issues bob the read cap
   expect(caps.canRead("did:ng:o:prot", "bob")).toBe(true);
 });
 
@@ -25,6 +25,25 @@ test("private documents: owner only", () => {
   expect(caps.canRead("did:ng:o:priv", null)).toBe(false);
 });
 
+test("protectedDocsOf surfaces an owner's protected documents for directed grants", () => {
+  const caps = new CapRegistry();
+  caps.open("did:ng:o:prot1", "protected", "alice");
+  caps.open("did:ng:o:prot2", "protected", "alice");
+  caps.open("did:ng:o:pub", "public", "alice"); // not protected → excluded
+  caps.open("did:ng:o:priv", "private", "alice"); // not protected → excluded
+  caps.open("did:ng:o:bob", "protected", "bob"); // other owner → excluded
+  expect(caps.protectedDocsOf("alice").sort()).toEqual([
+    "did:ng:o:prot1",
+    "did:ng:o:prot2",
+  ]);
+  expect(caps.protectedDocsOf("bob")).toEqual(["did:ng:o:bob"]);
+  expect(caps.protectedDocsOf("carol")).toEqual([]);
+  // A directed grant on one of them makes the reader read that doc only.
+  caps.grantRead("did:ng:o:prot1", "carol");
+  expect(caps.canRead("did:ng:o:prot1", "carol")).toBe(true);
+  expect(caps.canRead("did:ng:o:prot2", "carol")).toBe(false);
+});
+
 test("write is restricted to write-cap holders; the creator always holds it", () => {
   const caps = new CapRegistry();
   caps.open("did:ng:o:pub", "public", "alice");