web+host: fix raw! HTML dropped in client SX render (dom-parse-html returned a NodeList)

dom-parse-html returned body.childNodes — a NodeList, not a Node — so the client
SX render did appendChild(NodeList) and threw "Argument 1 does not implement
interface Node", silently dropping every raw! HTML block (e.g. a post's <article>
body). It surfaced only now because the blog renders fragments client-side
(text/sx) since this session; before, fragments were server HTML so sx-render
never ran on raw!. The error is caught/non-fatal, and the spa-check suite only
asserted the footer + URL behaviour, so it passed through a dropped post body.

- dom-parse-html now returns a DocumentFragment (moves the parsed nodes in): a
  real Node, appendChild-able as one unit, and queryable — which also fixes the
  already-broken hs-htmx callers that did (dom-query doc ...) / (dom-first-child
  doc) on what was a NodeList.
- spa-check: assert #content article is visible after a boosted nav, so a dropped
  post body fails the suite (closes the test gap).
- .sxbc regenerated; bundle dom.sx synced to canonical web/lib/dom.sx.

Verified: spa-check 4/4 (incl. the new article assertion).

lib/host/playwright/spa-check.spec.js

@@ -51,6 +51,10 @@ test.describe('blog SPA', () => {
     expect(await page.evaluate(() => window.__noReload)).toBe(true);     // no reload
     // content was swapped into #content (a post page carries the post footer)
     await expect(page.locator('#content')).toContainText(/all posts/i, { timeout: 15000 });
+    // the post BODY itself rendered — the <article> comes from raw! HTML, which
+    // exercises the client SX raw-HTML path (dom-parse-html). If that drops the
+    // content (NodeList-vs-Node bug), the footer still shows but this fails.
+    await expect(page.locator('#content article').first()).toBeVisible({ timeout: 15000 });
   });
 
   test('back button restores the listing', async ({ page }) => {