websocat reads stdin line-by-line and waits for \n before sending each chunk.
LSP JSON bodies have no trailing \n, causing a deadlock: websocat holds the
body, the server waits for the body, LSP4IJ waits for the response.
lsp_bridge.py reads complete Content-Length-framed messages before sending,
then sends each as a single binary WebSocket frame. This fixes autocomplete
in IntelliJ IDEA via LSP4IJ.
