Restore hyperscript work on stable site base (908f4f80)

Reset to last known-good state (908f4f80) where links, stepper, and
islands all work, then recovered all hyperscript implementation,
conformance tests, behavioral tests, Playwright specs, site sandbox,
IO-aware server loading, and upstream test suite from f271c88a.

Excludes runtime changes (VM resolve hook, VmSuspended browser handler,
sx_ref.ml guard recovery) that need careful re-integration.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/playwright/helpers.js

@@ -43,4 +43,89 @@ function trackErrors(page) {
   };
 }
 
-module.exports = { BASE_URL, waitForSxReady, loadPage, trackErrors };
+/**
+ * Universal smoke checks for any SX page.
+ * Runs 10 assertions that every page should pass.
+ * Returns { pass: boolean, failures: string[] }.
+ */
+async function universalSmoke(page) {
+  const failures = [];
+  const warnings = [];
+
+  // 1. Not blank — #sx-content has substantial text
+  const contentLen = await page.evaluate(() => {
+    const el = document.querySelector('#sx-content') || document.body;
+    return el.textContent.length;
+  });
+  if (contentLen < 50) failures.push(`blank page (${contentLen} chars)`);
+
+  // 2. Has heading (soft — some index/demo pages legitimately lack headings)
+  const headingCount = await page.locator('h1, h2, h3, h4').count();
+  if (headingCount === 0) warnings.push('no heading (h1-h4)');
+
+  // 3. Title set
+  const title = await page.title();
+  if (!title || title === 'about:blank') failures.push(`title not set: "${title}"`);
+
+  // 4. Layout intact — #sx-nav exists
+  const navExists = await page.locator('#sx-nav').count();
+  if (navExists === 0) failures.push('no #sx-nav');
+
+  // 5. No duplicate structural IDs
+  const dupes = await page.evaluate(() => {
+    const ids = ['sx-nav', 'sx-content', 'main-panel'];
+    return ids.filter(id => document.querySelectorAll('#' + id).length > 1);
+  });
+  if (dupes.length > 0) failures.push(`duplicate IDs: ${dupes.join(', ')}`);
+
+  // 6. No broken hrefs — no [object Object] in links
+  const brokenLinks = await page.evaluate(() => {
+    return [...document.querySelectorAll('a[href]')]
+      .filter(a => a.href.includes('[object Object]'))
+      .length;
+  });
+  if (brokenLinks > 0) failures.push(`${brokenLinks} broken [object Object] links`);
+
+  // 7. CSSX present
+  const cssxCount = await page.locator('style[id="sx-css"], style[data-sx-css]').count();
+  if (cssxCount === 0) failures.push('no CSSX style tag');
+
+  // 8. No hard SX leaks — raw dicts, raw SX elements, [object Object]
+  //    (Unresolved components like ~tw and CSSX :tokens are expected in SSR-only mode)
+  const leaks = await page.evaluate(() => {
+    const skip = new Set();
+    document.querySelectorAll('code, pre, script, style, [data-sx-source]').forEach(el => {
+      el.querySelectorAll('*').forEach(d => skip.add(d));
+      skip.add(el);
+    });
+    const walker = document.createTreeWalker(document.body, NodeFilter.SHOW_TEXT, {
+      acceptNode: (node) => {
+        let p = node.parentElement;
+        while (p) {
+          if (skip.has(p)) return NodeFilter.FILTER_REJECT;
+          p = p.parentElement;
+        }
+        return NodeFilter.FILTER_ACCEPT;
+      }
+    });
+    let text = '';
+    let n;
+    while (n = walker.nextNode()) text += n.textContent;
+    const found = [];
+    if (/\{:(?:type|tag|expr|spreads|attrs)\s/.test(text)) found.push('raw-dict');
+    if (/\((?:div|span|h[1-6]|p|a|button)\s+:(?:class|id|style)/.test(text)) found.push('raw-sx-element');
+    if (/\[object Object\]/.test(text)) found.push('object-Object');
+    return found;
+  });
+  if (leaks.length > 0) failures.push(`SX leaks: ${leaks.join(', ')}`);
+
+  // 9. No console errors (checked by caller via trackErrors)
+  // — intentionally not checked here; caller should use trackErrors()
+
+  // 10. Hydration (optional — pages served via route interception may not hydrate)
+  // — checked by caller if applicable
+
+  return { pass: failures.length === 0, failures, warnings };
+}
+
+module.exports = { BASE_URL, waitForSxReady, loadPage, trackErrors, universalSmoke };