Release v1.4.18 with performance optimization and deep bug fixes

- Optimize session cloning: replace JSON.parse/stringify with shallow spread (~10x faster for large queues)
- Convert blocking fs.existsSync/statSync to async on download hot path
- Fix EXDEV cross-device rename in sync saveSettings/saveSession (network drive support)
- Fix double-delete bug in applyCompletedCleanupPolicy (package_done + immediate)
- Fix dangling runPackageIds/runCompletedPackages in removePackageFromSession
- Fix AdmZip partial extraction: use overwrite mode for external fallback
- Add null byte stripping to sanitizeFilename (path traversal prevention)
- Add 5MB size limit for hash manifest files (OOM prevention)
- Add 256KB size limit for link artifact file content check
- Deduplicate cleanup code via centralized removePackageFromSession

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/extractor.test.ts

@@ -421,4 +421,30 @@ describe("extractor", () => {
     expect(result.failed).toBe(0);
     expect(result.extracted).toBe(0);
   });
+
+  it("rejects zip entries with path traversal", async () => {
+    const root = fs.mkdtempSync(path.join(os.tmpdir(), "rd-extract-"));
+    tempDirs.push(root);
+    const packageDir = path.join(root, "pkg");
+    const targetDir = path.join(root, "out");
+    fs.mkdirSync(packageDir, { recursive: true });
+
+    const zip = new AdmZip();
+    zip.addFile("safe.txt", Buffer.from("safe"));
+    zip.addFile("../escaped.txt", Buffer.from("malicious"));
+    zip.writeZip(path.join(packageDir, "traversal.zip"));
+
+    const result = await extractPackageArchives({
+      packageDir,
+      targetDir,
+      cleanupMode: "none",
+      conflictMode: "overwrite",
+      removeLinks: false,
+      removeSamples: false
+    });
+
+    expect(result.extracted).toBe(1);
+    expect(fs.existsSync(path.join(targetDir, "safe.txt"))).toBe(true);
+    expect(fs.existsSync(path.join(root, "escaped.txt"))).toBe(false);
+  });
 });