feat: add fuzz testing infrastructure and fix nostrEventSchemas crash

- Added `scripts/agent/fuzz-schemas.mjs`, `fuzz-dm.mjs`, `fuzz-magnet.mjs` and `fuzz-setup.mjs`.
- Fixed crash in `js/nostrEventSchemas.js` (buildAdminListEvent log and getNostrEventSchema type check).
- Added crash reproducers in `examples/reproducers/`.
- Fuzzers output reports to `artifacts/`.
- Updated fuzzers to deduplicate crashes and safely stringify inputs.

scripts/agent/fuzz-setup.mjs

@@ -0,0 +1,55 @@
+import crypto from 'node:crypto';
+
+// Mock localStorage
+const localStorageStore = new Map();
+const localStorageMock = {
+  getItem: (key) => localStorageStore.get(String(key)) ?? null,
+  setItem: (key, value) => localStorageStore.set(String(key), String(value)),
+  removeItem: (key) => localStorageStore.delete(String(key)),
+  clear: () => localStorageStore.clear(),
+  key: (index) => Array.from(localStorageStore.keys())[index] ?? null,
+  get length() {
+    return localStorageStore.size;
+  },
+};
+
+// Mock window
+const windowMock = {
+  localStorage: localStorageMock,
+  crypto: {
+    getRandomValues: (buffer) => crypto.getRandomValues(buffer),
+    subtle: crypto.webcrypto.subtle,
+  },
+  location: {
+    protocol: 'https:',
+    hostname: 'bitvid.network',
+    href: 'https://bitvid.network/',
+  },
+};
+
+// Polyfill globals
+if (typeof globalThis.window === 'undefined') {
+  globalThis.window = windowMock;
+}
+
+if (typeof globalThis.localStorage === 'undefined') {
+  globalThis.localStorage = localStorageMock;
+}
+
+if (typeof globalThis.crypto === 'undefined') {
+  globalThis.crypto = windowMock.crypto;
+}
+
+if (typeof globalThis.WebSocket === 'undefined') {
+    globalThis.WebSocket = class WebSocket {
+        constructor(url) {
+            this.url = url;
+            this.readyState = 0;
+        }
+        send() {}
+        close() {}
+    };
+}
+
+// Mock bitvid-specific globals if needed (though config.js sets them on window)
+globalThis.bitvidNostrEventOverrides = {};