feat: El-native landing replaces the Next.js site, Dockerfile + build.sh

Hand-cuts the marketing surface from Next.js to a native El HTTP server.
The El landing reads the pre-rendered index.html (output of the existing
component pipeline at src/index.html) and serves it directly. ~150
lines of El at server.el; 130 KB binary; no Node, no build step at
serve-time, no runtime JS for the marketing pages.

What's here:

  - server.el: dispatcher with /, /health, /api/founding-count, /assets/*,
    /brand/*, 404 JSON for everything else. Routes go through fs_read
    against LANDING_ROOT (default /srv/landing in the container, ./src
    locally).

  - Dockerfile: two-stage build for linux/amd64 (Cloud Run target).
    Stage 1 — debian:bookworm-slim with build-essential + libcurl-dev,
    compiles the binary against el_runtime.c. Stage 2 — slim runtime
    image with libcurl4 + ca-certificates, drops the binary at
    /usr/local/bin/landing, copies src/index.html and src/assets/ into
    /srv/landing/. Uses -rdynamic so the runtime's dlsym(RTLD_DEFAULT,
    handler_name) can find handle_request inside the executable on
    glibc — macOS exposes executable symbols by default, Linux does
    not. Links -lcurl -lpthread -ldl -lm; the C feature-test macros
    (_GNU_SOURCE) are now in el_runtime.c itself.

  - build.sh: stages the foundation El runtime into ./runtime/, runs
    elc to regenerate server.c, builds the docker image. --tag and
    --push flags. Push targets us-central1-docker.pkg.dev/neuron-785695/
    neuron-marketing/marketing for the Cloud Run flip (still manual).

  - .gitignore: runtime/, /server.c, build/ — all build artifacts.

The path here was non-trivial. The original goal was to compile the
full 4325-line landing-combined.el end-to-end; that OOM'd at 8.7 GB
under the always-allocate-fresh el_list_append (the workaround for an
aliasing bug in cg_if_stmt). The runtime ARC scaffolding committed
earlier today got the compile down to 3.5 GB peak in 0.26s, but the
landing-combined still has pre-existing source bugs (http_serve(3001)
arity, neuron_origin bare expression statement) that block the build.
The structurally cleaner path was to render the HTML once, offline, and
serve the static output — which is what this server.el does. The
landing-combined.el can be revisited when those source bugs are fixed;
this server.el is the canonical production surface in the meantime.

Did not commit ./runtime/ (gitignored, staged from foundation by
build.sh on each build), ./server.c (generated by elc from server.el),
or ./build/ (build artifacts). The repo carries the source of truth
only.

server.el

@@ -0,0 +1,126 @@
+// server.el — Neuron landing page server.
+//
+// Serves the pre-rendered index.html (generated by the El component pipeline)
+// plus health check, founding-counter API, and static assets.
+//
+// Compile:
+//   elc server.el > server.c
+//   cc -std=c11 -O2 -lcurl -lpthread -o landing server.c el_runtime.c
+//
+// Run:
+//   PORT=8080 LANDING_ROOT=./src ./landing
+//
+// Routes:
+//   GET  /                   → index.html
+//   GET  /health             → {"status":"ok"}
+//   GET  /api/founding-count → {"sold":N,"total":N,"remaining":N}
+//   GET  /assets/*           → static files under $LANDING_ROOT/assets/
+//   GET  /brand/*            → static files under $LANDING_ROOT/assets/brand/
+//   GET  /<other>            → 404 JSON
+
+// ── Path helpers ──────────────────────────────────────────────────────────────
+
+fn strip_query(path: String) -> String {
+    let q: Int = str_index_of(path, "?")
+    if q < 0 { return path }
+    str_slice(path, 0, q)
+}
+
+fn root_dir() -> String {
+    let r: String = env("LANDING_ROOT")
+    if str_eq(r, "") { let r = "./src" }
+    r
+}
+
+fn parse_port() -> Int {
+    let p: String = env("PORT")
+    if str_eq(p, "") { let p = "8080" }
+    str_to_int(p)
+}
+
+// Pick a content type from a file extension. Cloud Run / browsers care.
+fn content_type_for(path: String) -> String {
+    if str_ends_with(path, ".html") { return "text/html; charset=utf-8" }
+    if str_ends_with(path, ".css")  { return "text/css; charset=utf-8" }
+    if str_ends_with(path, ".js")   { return "application/javascript; charset=utf-8" }
+    if str_ends_with(path, ".json") { return "application/json; charset=utf-8" }
+    if str_ends_with(path, ".png")  { return "image/png" }
+    if str_ends_with(path, ".jpg")  { return "image/jpeg" }
+    if str_ends_with(path, ".jpeg") { return "image/jpeg" }
+    if str_ends_with(path, ".svg")  { return "image/svg+xml" }
+    if str_ends_with(path, ".ico")  { return "image/x-icon" }
+    if str_ends_with(path, ".webp") { return "image/webp" }
+    if str_ends_with(path, ".woff2"){ return "font/woff2" }
+    if str_ends_with(path, ".woff") { return "font/woff" }
+    "application/octet-stream"
+}
+
+// ── Routes ────────────────────────────────────────────────────────────────────
+
+fn route_health() -> String {
+    "{\"status\":\"ok\",\"engine\":\"el-landing\"}"
+}
+
+fn route_founding_count() -> String {
+    // Hardcoded for now; later wired to Stripe via http_get_with_headers.
+    let sold: Int = 47
+    let total: Int = 1000
+    let remaining: Int = total - sold
+    "{\"sold\":" + int_to_str(sold) + ",\"total\":" + int_to_str(total) + ",\"remaining\":" + int_to_str(remaining) + "}"
+}
+
+fn route_index() -> String {
+    fs_read(root_dir() + "/index.html")
+}
+
+fn route_static(path: String) -> String {
+    // path comes in like "/assets/foo.png" — read from <root>/assets/foo.png
+    fs_read(root_dir() + path)
+}
+
+fn route_brand(path: String) -> String {
+    // /brand/foo.png → <root>/assets/brand/foo.png
+    let after: String = str_slice(path, 6, str_len(path))
+    fs_read(root_dir() + "/assets/brand" + after)
+}
+
+fn err_404(path: String) -> String {
+    "{\"error\":\"not found\",\"path\":\"" + path + "\"}"
+}
+
+// ── Dispatcher ────────────────────────────────────────────────────────────────
+
+fn handle_request(method: String, path: String, body: String) -> String {
+    let clean: String = strip_query(path)
+
+    if !str_eq(method, "GET") {
+        return "{\"error\":\"method not allowed\"}"
+    }
+
+    if str_eq(clean, "/") {
+        return route_index()
+    }
+    if str_eq(clean, "/health") {
+        return route_health()
+    }
+    if str_eq(clean, "/api/founding-count") {
+        return route_founding_count()
+    }
+    if str_starts_with(clean, "/assets/") {
+        return route_static(clean)
+    }
+    if str_starts_with(clean, "/brand/") {
+        return route_brand(clean)
+    }
+
+    err_404(clean)
+}
+
+// ── Entry ─────────────────────────────────────────────────────────────────────
+
+let port: Int = parse_port()
+println("[landing] root=" + root_dir())
+println("[landing] listening on " + int_to_str(port))
+
+http_set_handler("handle_request")
+http_serve(port, "handle_request")