chore: checkpoint web Blender feature-gap work, docs and tests

- update native web_engine sources and rebuilt wasm artifacts
- add task cards, status notes and tooling scripts
- add web e2e specs, tutorial UI sources and tutorial assets
- sync golden task manifests and audit records

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

web/tests/e2e/reducer-tutorial-accessibility.spec.ts

@@ -0,0 +1,37 @@
+import AxeBuilder from "@axe-core/playwright";
+import { test, expect } from "@playwright/test";
+
+type AxeViolation = { id: string; help: string; impact?: string | null; nodes: Array<{ target?: unknown; failureSummary?: string }> };
+
+const severity = (violations: AxeViolation[]) =>
+  violations.filter((violation) => violation.impact === "critical" || violation.impact === "serious")
+    .map((violation) => `${violation.id}: ${violation.help} (${violation.nodes.length} nodes) :: ${violation.nodes.slice(0, 6).map((node) => `${JSON.stringify(node.target)} ${node.failureSummary ?? ""}`).join(" | ")}`);
+
+test("reducer tutorial landing, React course tree and live hierarchy tree are accessible", async ({ page }) => {
+  test.setTimeout(240_000);
+  await page.goto("/?tutorial=reducer");
+  await expect(page.getByRole("heading", { name: /从零制作/ })).toBeVisible({ timeout: 60_000 });
+  const courseTree = page.getByRole("tree", { name: "二级减速器课程结构" });
+  await expect(courseTree).toBeVisible({ timeout: 30_000 });
+  await expect(courseTree.getByRole("treeitem").first()).toBeVisible();
+  const landing = await new AxeBuilder({ page }).withTags(["wcag2a", "wcag2aa", "wcag21a", "wcag21aa", "wcag22aa"]).analyze();
+  expect(severity(landing.violations)).toEqual([]);
+
+  await page.getByRole("button", { name: /开始学习/ }).click();
+  const panel = page.locator('[data-course="reducer"]');
+  await expect(panel).toBeVisible({ timeout: 120_000 });
+  await expect(page.getByRole("button", { name: /^下一步/ })).toBeEnabled({ timeout: 180_000 });
+  await page.getByRole("button", { name: /^下一步/ }).click();
+  await expect(page.locator('[data-tutorial-step="housing-block"]')).toBeVisible();
+  await expect(panel.locator(".tutorial-checks")).toHaveAttribute("aria-live", "polite");
+
+  // The assembly step renders the live React hierarchy tree from SceneIR.
+  await page.getByRole("button", { name: "查看课程目录" }).click();
+  await page.locator("nav.tutorial-steps button", { hasText: "轴组件 Empty" }).click();
+  await expect(page.locator('[data-tutorial-step="shaft-assemblies"]')).toBeVisible();
+  const hierarchy = page.getByRole("tree", { name: "场景装配层级" });
+  await expect(hierarchy).toBeVisible();
+  await expect(hierarchy.getByRole("treeitem").first()).toBeVisible();
+  const overlay = await new AxeBuilder({ page }).include(".parts-tutorial-overlay").withTags(["wcag2a", "wcag2aa", "wcag21a", "wcag21aa", "wcag22aa"]).analyze();
+  expect(severity(overlay.violations)).toEqual([]);
+});