feat: add Nostr channel plugin and onboarding install defaults

Co-authored-by: joelklabo <joelklabo@users.noreply.github.com>

extensions/nostr/test/setup.ts

@@ -0,0 +1,5 @@
+// Test setup file for nostr extension
+import { vi } from "vitest";
+
+// Mock console.error to suppress noise in tests
+vi.spyOn(console, "error").mockImplementation(() => {});