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>

changes/http-namespace.md

@@ -0,0 +1,20 @@
+bump: minor
+type: feat
+**HTTP client standard library (#6).** `Http.*` — a poll-based HTTP/HTTPS client
+for out-of-band data (leaderboards, cloud saves, remote config, telemetry,
+downloads). `Http.get` / `Http.post` / `Http.request` start a request (or
+`Http.open` + `Http.set` headers + `Http.body` + `Http.send` to build one up);
+`Http.poll` returns `-1` while pending, `0` on error, else the status code, so
+the frame never blocks; `Http.status` / `ok` / `text` / `body_len` / `header`
+read the reply, and `Http.free` releases it. TLS is the system's, on by default
+with certificate verification — an `https://` URL just works. Pairs with the
+`Json.*` companion (already shipped in #44): `Json.parse(Http.text(h))`.
+
+The transport (`runtime/native/http.ll`) drives NSURLConnection through the objc
+runtime's C ABI on a detached pthread — same hand-written-IR, no-ObjC/no-C style
+as cocoa.ll — and is spliced with Foundation only when a program uses `Http.*`
+(macOS for now). The response parser (`Http.parse`, header lookup) is pure Ludic
+and portable, so the suite exercises it offline with no network. HTTP depends on
+the network and wall clock and is explicitly out-of-band: it must never feed the
+deterministic lockstep/replay simulation, like `Net.*` and `Time.now`. Also adds
+the `\r` string/char escape the protocol needs.