Deno 2.9

Deno 2.9 introduces `deno desktop` for building native desktop apps from web technologies, producing single distributable binaries with webview or CEF backends. The release adds first-class migration from npm/pnpm/yarn/Bun lockfiles, CSS module imports, and major test runner improvements including snapshot testing, parameterized tests (`Deno.test.each`), change-aware test selection, retries, coverage thresholds, and CI sharding. Performance gains include 2x faster cold startup (34ms → 17ms), 3x lower memory usage under load, and improved HTTP throughput. Supply chain security gets a 24-hour minimum dependency age enabled by default and an opt-in `no-downgrade` trust policy. `deno compile` gains `--bundle` for smaller binaries, `deno task` adds input-based caching, and Node.js 26 compatibility is now the target. Web Cryptography expands with post-quantum algorithms (ML-KEM, ML-DSA, SLH-DSA), ChaCha20-Poly1305, and SHA-3 family support.