Add Server-Sent Events support to the El runtime. El v2 handlers can now
hold HTTP connections open and push events in real time.
New builtins in el_seed.c:
__http_conn_fd() — retrieve raw fd from thread-local set by worker
__http_sse_open(fd) — send SSE headers (text/event-stream), keep-alive
__http_sse_send(fd, data) — write "data: <data>\n\n" frame
__http_sse_close(fd) — close the connection fd
http_worker_v2 in legacy/el_runtime.c now:
- stashes the fd via el_seed_set_http_conn_fd() before calling the handler
- detects the "__sse__" sentinel return value to skip http_send_response
and skip close(fd) — SSE handler took ownership of the fd
- clears the thread-local after the handler returns
El wrappers added to runtime/http.el:
http_conn_fd() http_sse_open(fd) http_sse_send(fd, data)
http_sse_close(fd) http_sse_sentinel()
Thin El wrappers over seed primitives that form the public HTTP API for
El programs. Covers GET/POST/DELETE, header-map variants, binary streaming
to file, form-auth, v1/v2 server dispatch, and http_response envelope
construction. Documents two new seed primitives needed: __http_do_map and
__http_do_map_to_file (ElMap-accepting variants to avoid needing map
iteration in El).
Will Anderson