Introduces El's first-class threading primitives built on the seed layer's
__thread_create/__thread_join/mutex ops. parallel_map is the key deliverable:
spawns one thread per item, joins in order — replaces bash fan-out for room
dispatch and any other concurrent HTTP workload.
Thin El wrappers over seed JSON primitives (json_get, json_get_raw,
json_parse, json_stringify, json_set, json_array_len, json_array_get,
json_array_get_string) plus typed extractors (json_get_string/int/float/bool)
and pure-El builders (json_build_object, json_build_array,
json_escape_string) that require no seed call.
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