Bump to 0.17.0: streaming works in the default server; HEAD headers-only; opt-in gzip

- Streaming responses (http-response/file, SSE) now work from a bare http-serve without with-async (http-server-start self-installs a scheduler). - HEAD returns identical status + headers with zero body bytes. - Opt-in automatic gzip via the gzip: server option (default off). - Minor bump: new public API (gzip:) + changed default server behavior; also aligns the package version to its ^0.17 toolchain target.