Baseline: Ludic compiler + toolchain, Phase 1 syntax fixes complete

Self-hosted compiler (selfhost/*.ludic), runtime, examples, editor tooling,
and docs. Phase 1 of the syntax-redesign cohesion pass has landed:
edge-system fix, signature-query, when-alias, and the documentation truth-pass.
Suite green (14/14), C-free bootstrap fixpoint holds.

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

tools/ludic-web/run.mjs

@@ -0,0 +1,106 @@
+// ============================================================================
+// tools/ludic-web/run.mjs — run a headless Ludic wasm build under Node.
+//
+//     node tools/ludic-web/run.mjs build/web/snake_headless.wasm --stdin=ddss
+//
+// The point of this runner is the regression it makes possible: the same game,
+// the same input, compiled once for the host and once for wasm32, has to render
+// the same frame. Ludic is fixed-point and its RNG is seeded, so "the same" here
+// means byte-identical PPM — which is a much stronger check on the wasm backend
+// than "it started".
+//
+// It shares runtime/web/platform.js's Host: files, stdin, stdout and the clock
+// are identical services whichever host provides them. Only the window differs,
+// and a headless build has none.
+// ============================================================================
+import { readFileSync, writeFileSync, existsSync } from 'node:fs';
+import { Host, ExitSignal } from '../../runtime/web/platform.js';
+
+const args = process.argv.slice(2);
+const modulePath = args.find((a) => !a.startsWith('--'));
+const stdin = (args.find((a) => a.startsWith('--stdin=')) || '--stdin=').slice(8);
+const maxFrames = Number((args.find((a) => a.startsWith('--frames=')) || '--frames=100000').slice(9));
+
+if (!modulePath) {
+  console.error('usage: run.mjs <module.wasm> [--stdin=keys] [--frames=n]');
+  process.exit(2);
+}
+
+// Files, backed by the real filesystem: a headless build reads its assets and
+// writes out.ppm exactly where the native headless binary does.
+class NodeFiles {
+  constructor() { this.open = new Map(); this.next = 1; }
+
+  fopen(path, mode) {
+    const h = this.next++;
+    if (mode.includes('w') || mode.includes('a')) {
+      this.open.set(h, { path, write: true, chunks: [], size: 0, pos: 0 });
+      return h;
+    }
+    if (!existsSync(path)) return 0;
+    this.open.set(h, { path, write: false, data: new Uint8Array(readFileSync(path)), pos: 0 });
+    return h;
+  }
+
+  fread(h, dst, want) {
+    const f = this.open.get(h);
+    if (!f || f.write) return 0;
+    const n = Math.max(0, Math.min(want, f.data.length - f.pos));
+    dst.set(f.data.subarray(f.pos, f.pos + n));
+    f.pos += n;
+    return n;
+  }
+
+  fwrite(h, src, n) {
+    const f = this.open.get(h);
+    if (!f || !f.write) return 0;
+    f.chunks.push(src.slice(0, n));
+    f.size += n; f.pos += n;
+    return n;
+  }
+
+  fclose(h) {
+    const f = this.open.get(h);
+    if (!f) return;
+    if (f.write) {
+      const all = new Uint8Array(f.size);
+      let at = 0;
+      for (const c of f.chunks) { all.set(c, at); at += c.length; }
+      writeFileSync(f.path, all);
+    }
+    this.open.delete(h);
+  }
+
+  fseek(h, off, whence) {
+    const f = this.open.get(h);
+    if (!f) return -1;
+    const end = f.write ? f.size : f.data.length;
+    const base = whence === 1 ? f.pos : whence === 2 ? end : 0;
+    f.pos = Math.max(0, Math.min(end, base + off));
+    return 0;
+  }
+
+  ftell(h) { const f = this.open.get(h); return f ? f.pos : -1; }
+}
+
+const host = new Host({ files: new NodeFiles(), stdin });
+const { instance } = await WebAssembly.instantiate(readFileSync(modulePath), { env: host.imports() });
+host.bind(instance.exports.memory);
+
+const { ludic_boot, ludic_frame, ludic_alive, ludic_teardown } = instance.exports;
+
+let frames = 0;
+try {
+  ludic_boot();
+  while (host.running && ludic_alive() && frames < maxFrames) { ludic_frame(); frames++; }
+  ludic_teardown();
+} catch (e) {
+  if (!(e instanceof ExitSignal)) throw e;
+}
+host.flush();
+
+if (frames >= maxFrames) {
+  console.error(`ludic-web: stopped after ${maxFrames} frames (the game never ended)`);
+  process.exit(1);
+}
+process.exit(host.exitCode ?? 0);