M15.1: web build (eframe wasm) + xtask web

- apps/effectcraft-web (L6): eframe web runner booting the shared EffectcraftApp with a browser
  session: in-memory file table, <input type=file> pickers and drag-and-drop for open/import,
  downloads for Save and Render Queue outputs (several files as one stored .zip), and the
  window.effectcraft promise API over the control channel. Demo project on start.
- wasm32 runtime fixes: web-time for Instant/SystemTime (render, engine, export, ui-egui);
  Frames renders queued jobs on the UI thread (Frames::pump) instead of a thread pool;
  Render Queue runs inline; relative outputs resolve under / ; control PNGs inline.
- effectcraft-export: per-job output Sink (files to memory instead of disk); host FileExporter
  carries it; test that sink exports touch no file.
- xtask web [--dev] [--serve PORT] (wasm-bindgen 0.2.129, optional wasm-opt, COOP/COEP server);
  effectcraft-web in WEB_CRATES. docs/web.md, headless Chrome smoke test, favicon (+attribution).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

apps/effectcraft-web/web/favicon.svg

@@ -0,0 +1,8 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64">
+  <!-- EffectCraft mark (original work): the header logo of crates/ui-egui/src/header.rs as SVG:
+       a navy rounded square split blue/violet with a white keyframe diamond. -->
+  <rect x="0" y="0" width="64" height="64" rx="12" fill="#1d2b5e"/>
+  <path d="M14 4 H32 V60 H14 A10 10 0 0 1 4 50 V14 A10 10 0 0 1 14 4 Z" fill="#2d8ceb"/>
+  <path d="M32 4 H50 A10 10 0 0 1 60 14 V50 A10 10 0 0 1 50 60 H32 Z" fill="#8e6bff"/>
+  <path d="M32 15.4 L48.6 32 L32 48.6 L15.4 32 Z" fill="#ffffff"/>
+</svg>

apps/effectcraft-web/web/favicon.svg.attribution

@@ -0,0 +1,9 @@
+asset:        favicon.svg
+title:        EffectCraft web app icon (favicon)
+author:       EffectCraft contributors
+source:       original work
+license:      MIT OR Apache-2.0
+added:        2026-10-01 by EffectCraft contributors (Claude agent, M15 web app)
+notes:        Hand-written SVG of the code-drawn EffectCraft mark (`paint_logo` in
+              crates/ui-egui/src/header.rs): a navy rounded square split into blue and violet halves
+              with a white keyframe diamond, from basic shapes. Not derived from any other product's icon.

apps/effectcraft-web/web/index.html

@@ -0,0 +1,64 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <meta name="color-scheme" content="dark">
+  <title>EffectCraft</title>
+  <link rel="icon" href="favicon.svg" type="image/svg+xml">
+  <style>
+    html, body { margin: 0; height: 100%; overflow: hidden; background: #1b1c1f; }
+    canvas { position: absolute; inset: 0; width: 100%; height: 100%; display: block; outline: none; }
+    #loading {
+      position: absolute; inset: 0; display: flex; flex-direction: column; gap: 14px;
+      align-items: center; justify-content: center; color: #c9c9cc;
+      font: 14px/1.4 system-ui, sans-serif; pointer-events: none;
+    }
+    #loading img { width: 56px; height: 56px; }
+    #loading .err { color: #ff8a7a; white-space: pre-wrap; max-width: 70ch; pointer-events: auto; }
+  </style>
+</head>
+<body>
+  <canvas id="effectcraft_canvas"></canvas>
+  <div id="loading"><img src="favicon.svg" alt=""><div id="status">Loading EffectCraft…</div></div>
+  <script type="module">
+    import init, * as ec from "./effectcraft_web.js";
+    const t0 = performance.now();
+    window.effectcraftLoad = {};
+    // The agent / test API: the desktop control channel as promises (docs/web.md).
+    window.effectcraft = {
+      request: (method, params) => ec.request(method, params ?? {}),
+      execute: (command, params) => ec.request("engine.execute", { command, params: params ?? {} }),
+      commands: () => ec.request("engine.commands", {}),
+      inspect: () => ec.request("ui.inspect", {}),
+      screenshot: (params) => ec.request("ui.screenshot", params ?? {}),
+      renderFrame: (params) => ec.request("render.frame", { base64: true, ...(params ?? {}) }),
+      files: () => ec.files(),
+      readFile: (path) => ec.readFile(path),
+      addFile: async (fileOrUrl, name) => {
+        let bytes;
+        if (typeof fileOrUrl === "string") {
+          bytes = new Uint8Array(await (await fetch(fileOrUrl)).arrayBuffer());
+          name = name ?? fileOrUrl.split("/").pop();
+        } else {
+          bytes = new Uint8Array(await fileOrUrl.arrayBuffer());
+          name = name ?? fileOrUrl.name;
+        }
+        return ec.addFile(name, bytes);
+      },
+      info: () => ({ ...ec.info(), crossOriginIsolated: self.crossOriginIsolated, load: window.effectcraftLoad }),
+    };
+    try {
+      await init();
+      window.effectcraftLoad.wasmMs = performance.now() - t0;
+      await ec.start("effectcraft_canvas");
+      window.effectcraftLoad.readyMs = performance.now() - t0;
+    } catch (e) {
+      const s = document.getElementById("status");
+      if (s) { s.className = "err"; s.textContent = "EffectCraft failed to start:\n" + (e && e.stack || e); }
+      window.effectcraftLoad.error = String(e);
+      throw e;
+    }
+  </script>
+</body>
+</html>