Lazy remote FST viewing over SSH: wellen wasm + HTTP Range proxy

To view a large remote FST without copying it, run wellen (compiled to wasm) locally and satisfy its synchronous positional-read import with synchronous XMLHttpRequest + Range header from a Web Worker, proxied through an ssh -L tunnel to a tiny Range-capable HTTP server on the remote host. With wellen's dynamic (non-static) load mode and an 8 KB buffer, a 57 MB FST opened in ~0.44 s reading only 166 KB, and a 400k-change signal loaded in ~0.65 s (~1 MB total) at ~36 ms average RTT; zoom/pan is then purely local. The cost is many small serial requests (~8 ms each), so larger reads or read-ahead are the next win. VCD can't benefit: wellen parses it sequentially, so every byte crosses the link. Gotcha: ssh host 'nohup server & ...; curl ...' can hang the ssh session; start servers with stdin from /dev/null and all output redirected, and check them in a separate call.