feat(client): generic shared-wallet shim surface (docs/storeRegistry/isolation/accounts)

Port the shared-wallet shim mechanics from the Festipod app into the
generic @ng-eventually/client library — zero app-specific knowledge, the
consumer injects the domain (entity->scope mapping, connections, storage).

New namespaces exposed from src/index.ts:
- docs      docCreate/sparqlUpdate/sparqlQuery via the REAL injected `ng`
            (getConfig().ng), never the public makeNg proxy — the JS-over-
            iframe double proxy breaks doc_create postMessage marshaling
            (DataCloneError). Validated hard constraint.
- storeRegistry  generic (account,scope)->NURI resolver, createEntityDoc/
            listEntityDocs + per-scope index, sharedWalletShim in the
            private_store, cache. Consumer wiring injected via
            configureStoreRegistry({ getSession, normalizeUser }).
- isolation  pure applyIsolation (public=all / protected=owner+connections
            / private=owner); accessors + connection graph injected.
- accounts  AccountStore (localStorage-backed faux login, storage injected)
            + normalizeUsername. React wrapper intentionally NOT ported.

polyfill.ts gains configureStoreRegistry/getStoreRegistryDeps + resetConfig.
36/36 bun test, tsc --noEmit rc=0.

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

packages/client/src/polyfill.ts

@@ -9,8 +9,22 @@
  */
 
 import type { NgLike, UseShapeLike, PrincipalId } from "./types";
+import type { RegistrySession } from "./store-registry";
 import { CapRegistry } from "./caps";
 
+/**
+ * Consumer-injected dependencies of the storeRegistry (polyfill-era). The
+ * registry itself is generic (it knows only native scopes); the consumer wires
+ * up how to reach the shared-wallet session and how to normalize a username
+ * used as the shim key. Removed at migration along with the whole shim.
+ */
+export interface StoreRegistryDeps {
+  /** Resolve the current shared-wallet session (id + private-store anchor). */
+  getSession: () => Promise<RegistrySession>;
+  /** Normalize a username for shim keying. Default: trim (identity-ish). */
+  normalizeUser?: (username: string) => string;
+}
+
 export interface EventuallyConfig {
   /** The REAL `@ng-org/web` `ng` (injected to avoid a hard import / alias loop). */
   ng: NgLike;
@@ -28,6 +42,7 @@ export interface EventuallyConfig {
 
 let cfg: EventuallyConfig | null = null;
 let currentUser: PrincipalId | null = null;
+let registryDeps: Required<StoreRegistryDeps> | null = null;
 /** The emulated ReadCap/WriteCap registry. Empty until the app declares caps;
  *  while it has no read policy the read filter passes through (no regression). */
 let caps = new CapRegistry();
@@ -43,6 +58,39 @@ export function getConfig(): EventuallyConfig {
   return cfg;
 }
 
+/** Reset the injected config back to un-configured (mainly for tests, so a
+ *  suite that calls configure() can restore the not-configured guard state). */
+export function resetConfig(): void {
+  cfg = null;
+  currentUser = null;
+}
+
+/**
+ * Wire the storeRegistry's consumer-injected dependencies (session + username
+ * normalization). Must be called before any storeRegistry.* use. Separate from
+ * {@link configure} because it's storeRegistry-specific and, like the shim,
+ * disappears at migration.
+ */
+export function configureStoreRegistry(deps: StoreRegistryDeps): void {
+  registryDeps = {
+    getSession: deps.getSession,
+    normalizeUser: deps.normalizeUser ?? ((u: string) => u.trim()),
+  };
+}
+
+/** @internal — used by the storeRegistry to reach its injected dependencies. */
+export function getStoreRegistryDeps(): Required<StoreRegistryDeps> {
+  if (!registryDeps) {
+    throw new Error("[ng-eventually] configureStoreRegistry() must be called before use");
+  }
+  return registryDeps;
+}
+
+/** Reset storeRegistry deps (mainly for tests). */
+export function resetStoreRegistry(): void {
+  registryDeps = null;
+}
+
 /** Set the current app-level user (the polyfill's notion of "who am I"). */
 export function setCurrentUser(id: PrincipalId | null): void {
   currentUser = id;