[auth] Fix "prepareStoredNsecSwitch is not a function" when switching to a saved nsec account

Switching (from NIP-07) to an added nsec account threw
"this.prepareStoredNsecSwitch is not a function".

Root cause: bindCoordinator binds every coordinator method to the Application
instance, so inside handleProfileSwitchRequest `this` === app. Its call to the
sibling `this.prepareStoredNsecSwitch(pubkey)` therefore resolves against the
Application and needs an app-level delegator (like handleProfileSwitchRequest,
handleModerationSettingsChange, and waitForIdentityRefresh all have). The #48 work
added prepareStoredNsecSwitch as a coordinator sibling but not its delegator, and
its tests only exercised authService.switchProfile — not the full app wiring — so
it slipped through.

Fix: add the app.prepareStoredNsecSwitch delegator (-> this._auth.prepareStoredNsecSwitch).

Tests: tests/profile-switch-coordinator-delegators.test.mjs (4) — asserts every
sibling handleProfileSwitchRequest calls via this.X exists as an app method.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

js/app.js

@@ -3330,6 +3330,17 @@ class Application {
     return this._auth.handleProfileSwitchRequest(...args);
   }
 
+  // Coordinator methods are bound to `this` (the Application) by bindCoordinator,
+  // so a sibling call like `this.prepareStoredNsecSwitch(...)` inside
+  // handleProfileSwitchRequest resolves against the Application — it needs this
+  // delegator to exist (like handleProfileSwitchRequest above). Without it,
+  // switching to a stored-nsec account threw "this.prepareStoredNsecSwitch is not
+  // a function".
+  async prepareStoredNsecSwitch(...args) {
+    this._initCoordinators();
+    return this._auth.prepareStoredNsecSwitch(...args);
+  }
+
   async waitForIdentityRefresh(...args) {
     this._initCoordinators();
     return this._auth.waitForIdentityRefresh(...args);

tests/profile-switch-coordinator-delegators.test.mjs

@@ -0,0 +1,50 @@
+// Switching to a saved nsec account threw "this.prepareStoredNsecSwitch is not a
+// function". Root cause: bindCoordinator binds every coordinator method to the
+// Application (`this` === app), so when a coordinator method calls a SIBLING via
+// `this.sibling(...)` it resolves against the Application — which therefore needs
+// an app-level delegator for that sibling. handleProfileSwitchRequest calls
+// this.prepareStoredNsecSwitch / this.handleModerationSettingsChange /
+// this.waitForIdentityRefresh; the nsec one was missing its delegator.
+//
+// test_integrity_note:
+//   change_type: ["new_tests"]
+//   scenarios:
+//     - id: SCN-profile-switch-coordinator-delegators
+//       given: "the Application class"
+//       when: "handleProfileSwitchRequest runs (bound to app) and calls siblings"
+//       then: "every sibling it calls exists as an app-level method/delegator"
+//   observable_outcomes:
+//     - "Application.prototype.prepareStoredNsecSwitch is a function"
+//     - "the other siblings it invokes are also app methods"
+//   determinism_controls:
+//     - "static prototype inspection; no network/clock/DOM"
+//   anti_cheat_rationale:
+//     prevents: ["hard-coded return value"]
+//   relaxation:
+//     did_relax_any_assertion: false
+
+import "./test-helpers/setup-localstorage.mjs";
+import test from "node:test";
+import { strict as assert } from "node:assert";
+import { Application } from "../js/app.js";
+
+// Every coordinator sibling that handleProfileSwitchRequest calls via `this.X`
+// must exist as an app-level method, because bindCoordinator binds the coordinator
+// methods to the Application instance.
+const REQUIRED_APP_METHODS = [
+  "handleProfileSwitchRequest",
+  "prepareStoredNsecSwitch", // was missing -> the reported bug
+  "handleModerationSettingsChange",
+  "waitForIdentityRefresh",
+];
+
+for (const name of REQUIRED_APP_METHODS) {
+  test(`Application exposes ${name}() so the bound profile-switch flow can call it`, () => {
+    assert.equal(
+      typeof Application.prototype[name],
+      "function",
+      `Application.prototype.${name} must be a function (coordinator siblings are ` +
+        `bound to app; handleProfileSwitchRequest calls it via this.${name}())`,
+    );
+  });
+}