feat(crash): add CrashWriter for local crash dumps (cap 20, prune oldest)

src/main/updater/crash-writer.js

@@ -0,0 +1,59 @@
+const fs = require('fs');
+const path = require('path');
+const MAX_DUMPS = 20;
+
+class CrashWriter {
+  constructor(dir) {
+    this.dir = dir;
+    this._counter = 0;
+    fs.mkdirSync(dir, { recursive: true });
+  }
+
+  handleUncaught(err, kind) {
+    try {
+      const filename = `${Date.now()}-${++this._counter}-${kind}.json`;
+      const payload = {
+        kind,
+        message: err && err.message,
+        stack: err && err.stack,
+        timestamp: new Date().toISOString(),
+      };
+      fs.writeFileSync(path.join(this.dir, filename), JSON.stringify(payload, null, 2));
+      this._prune();
+    } catch (writeErr) {
+      console.error('[crash-writer] dump write failed:', writeErr.message);
+    }
+  }
+
+  _prune() {
+    const files = fs.readdirSync(this.dir).sort();
+    while (files.length > MAX_DUMPS) {
+      const oldest = files.shift();
+      try { fs.unlinkSync(path.join(this.dir, oldest)); } catch (_) { /* ignore */ }
+    }
+  }
+
+  list() {
+    if (!fs.existsSync(this.dir)) return [];
+    return fs.readdirSync(this.dir)
+      .filter((f) => f.endsWith('.json'))
+      .sort()
+      .reverse()
+      .map((filename) => {
+        const full = path.join(this.dir, filename);
+        const data = JSON.parse(fs.readFileSync(full, 'utf-8'));
+        return { filename, ...data };
+      });
+  }
+
+  delete(filename) {
+    const full = path.join(this.dir, filename);
+    if (fs.existsSync(full)) fs.unlinkSync(full);
+  }
+
+  path() {
+    return this.dir;
+  }
+}
+
+module.exports = { CrashWriter };