feat(http): Http.* poll-based HTTP/HTTPS client over a native NSURLConnection backend (#6)

Adds the Http.* namespace and its transport, the HTTP client from #6. The JSON
companion the proposal called for already shipped as Json.* (#44).

- runtime/native/http.ll: the macOS transport — NSURLConnection driven through
  the objc runtime C ABI (no ObjC/C source), run on a detached pthread so the
  frame never blocks; TLS is the system's, on by default. A fixed slot pool holds
  each in-flight request; the worker publishes status/body/response behind an
  atomic done flag (release/acquire). Spliced + Foundation linked only when a
  program uses Http.*.
- runtime/native/http.ludic: the Http.* runtime — get/post/request, the
  open/set/body/send builder, poll/status/ok/text/body_len/header/free, plus a
  pure-Ludic response parser (Http.parse + case-insensitive header lookup) that
  is transport-independent and portable.
- compiler: Http.* dispatch, g_uses_http splice, hs_* transport intrinsics +
  declarations, the conditional Foundation link, and a new \r string/char escape
  the protocol needs.
- docs: a full docs/language/http section (16 pages); check-impl/check-docs green.
- test: examples/library/http.ludic self-asserts the parser offline (Darwin-gated
  build via the canonical path, since it links Foundation).

Verified end to end against real endpoints: HTTPS GET (200 + headers + body) and
POST (body + custom header). HTTP is out-of-band and never feeds the
deterministic sim. Reseeded; suites green (81 + 29).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/x/test.ludic

@@ -257,6 +257,16 @@ function cmd_test() -> int {
   feat_case("library/input_actions", "  xwa", "1 0 1 1 0 1 0", "input_actions.ludic (#7 action maps + rebinding + deterministic replay)")
   feat_case("library/input_device", "", "1 1 0 1 0 1 71 -71 5 1 3 1 2 1 0 0 1", "input_device.ludic (#50 multi-key held state + analog axis/vector + mouse + gamepad/touch + full-state replay)")
   feat_case("library/audio", "", "0 0 0 0 1", "audio.ludic (#22 Audio.* load/play/music/volume/pitch/stop/is_playing — headless no-op)")
+  # #6 Http.* — the client links Foundation (macOS-only), so build it through the
+  # canonical `ludicc -o` path (which wires the framework) and gate on Darwin. The
+  # run exercises the pure-Ludic response parser; no network is touched.
+  if is_darwin() {
+    if shq("LUDIC_HOME=. bin/ludicc examples/library/http.ludic -o /tmp/x_http_demo > /tmp/x_http.out 2>&1") {
+      let got = capture_line("/tmp/x_http_demo < /dev/null")
+      if (got == "200 1 5 hello 42 text/plain 404 0") { ok("http.ludic (#6 Http.parse/status/ok/text/header — pure response parser)") }
+      else { bad2("http.ludic", `got [{got}]`) }
+    } else { bad2("http.ludic build", capture_line("tail -1 /tmp/x_http.out")) }
+  }
 
   feat_case("events/recurse", "", "16", "recurse.ludic (EV6: re-entrant emit is depth-bounded, no runaway cycle)")
   net_case("events/scoped", "2")