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>

docs/language/http/_section.md

@@ -0,0 +1,9 @@
+---
+id: http
+title: Http
+order: 8
+---
+
+A poll-based HTTP / HTTPS client for out-of-band data — leaderboards, cloud saves, remote config, telemetry, downloads. Open a request with <a href="http-get.html"><code>Http.get</code></a> / <a href="http-post.html"><code>Http.post</code></a> (or <a href="http-open.html"><code>Http.open</code></a> to add headers first), then each frame call <a href="http-poll.html"><code>Http.poll</code></a> — it returns <code>-1</code> while pending, <code>0</code> on error, or the status code — so the frame never blocks. Read the reply with <a href="http-status.html"><code>Http.status</code></a> / <a href="http-ok.html"><code>ok</code></a> / <a href="http-text.html"><code>text</code></a> / <a href="http-header.html"><code>header</code></a>, and pair it with <code>Json.*</code> for (de)serialization. TLS is the system's, on by default.
+
+HTTP depends on the network and the wall clock, so — like <code>Net.*</code> and <code>Time.now</code> — it is <strong>out-of-band</strong> and must never feed the deterministic lockstep/replay simulation. The transport is macOS-only for now; the raw-response parser (<a href="http-parse.html"><code>Http.parse</code></a>) is pure and portable.