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-magnet.mjs

@@ -0,0 +1,120 @@
+import './fuzz-setup.mjs';
+import * as magnetUtils from '../../js/magnetUtils.js';
+import fs from 'node:fs';
+import path from 'node:path';
+import crypto from 'node:crypto';
+
+const REPRODUCER_DIR = 'examples/reproducers';
+const REPORT_FILE = 'artifacts/fuzz-report-magnet.json';
+
+const ITERATIONS = 5000;
+
+function getRandomString(length = 100) {
+    const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*()_+{}|:"<>?~`-=[]\;\',./% ';
+    let result = '';
+    for (let i = 0; i < length; i++) {
+        result += chars.charAt(Math.floor(Math.random() * chars.length));
+    }
+    return result;
+}
+
+function getRandomMagnet() {
+    const hash = getRandomString(40).replace(/[^0-9a-f]/gi, 'a');
+    return `magnet:?xt=urn:btih:${hash}&dn=${getRandomString(10)}&tr=${encodeURIComponent(getRandomString(20))}`;
+}
+
+async function run() {
+    console.log(`Starting fuzzing magnet utils for ${ITERATIONS} iterations...`);
+
+    const report = {
+        target: 'js/magnetUtils.js',
+        timestamp: new Date().toISOString(),
+        iterations: ITERATIONS,
+        crashes: [],
+    };
+
+    const uniqueCrashes = new Set();
+
+    const targets = [
+        { name: 'normalizeAndAugmentMagnet', fn: magnetUtils.normalizeAndAugmentMagnet, args: 2 },
+        { name: 'safeDecodeMagnet', fn: magnetUtils.safeDecodeMagnet, args: 1 },
+    ];
+
+    for (const { name, fn, args } of targets) {
+        for (let i = 0; i < ITERATIONS; i++) {
+            let input, options;
+
+            if (Math.random() < 0.3) {
+                input = getRandomMagnet();
+            } else if (Math.random() < 0.3) {
+                input = getRandomString(getRandomInt(200));
+            } else {
+                input = null; // or undefined, or object
+                if (Math.random() < 0.5) input = {};
+            }
+
+            if (args > 1) {
+                options = {
+                    webSeed: Math.random() < 0.5 ? getRandomString(20) : [getRandomString(20)],
+                    torrentUrl: getRandomString(20),
+                    extraTrackers: [getRandomString(20)],
+                    appProtocol: 'https:',
+                };
+                if (Math.random() < 0.1) options = null;
+                if (Math.random() < 0.1) options = "string";
+            }
+
+            try {
+                if (args === 1) {
+                    fn(input);
+                } else {
+                    fn(input, options);
+                }
+            } catch (err) {
+                const crashKey = `${name}:${err.message}`;
+                if (uniqueCrashes.has(crashKey)) {
+                    continue;
+                }
+                uniqueCrashes.add(crashKey);
+
+                let safeInput = "Could not stringify input";
+                try {
+                    safeInput = JSON.stringify(args === 1 ? input : { input, options });
+                } catch (e) {
+                    safeInput = "[Input causes JSON.stringify to throw]";
+                }
+
+                 const crashInfo = {
+                    function: name,
+                    input: safeInput,
+                    error: err.toString(),
+                    stack: err.stack,
+                };
+
+                const hash = crypto.createHash('sha256').update(JSON.stringify(crashInfo)).digest('hex').slice(0, 8);
+                const filename = `crash-magnet-${name}-${hash}.json`;
+                fs.writeFileSync(path.join(REPRODUCER_DIR, filename), JSON.stringify(crashInfo, null, 2));
+
+                report.crashes.push({
+                    file: filename,
+                    function: name,
+                    error: err.message
+                });
+
+                console.error(`[CRASH] ${name} failed! Saved to ${filename}`);
+            }
+        }
+    }
+
+    if (!fs.existsSync(path.dirname(REPORT_FILE))) {
+        fs.mkdirSync(path.dirname(REPORT_FILE), { recursive: true });
+    }
+    fs.writeFileSync(REPORT_FILE, JSON.stringify(report, null, 2));
+    console.log(`Fuzzing complete. Report saved to ${REPORT_FILE}. Crashes: ${report.crashes.length}`);
+}
+
+function getRandomInt(max) {
+  return Math.floor(Math.random() * max);
+}
+
+run();