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).

web/lib/dom.sx

@@ -359,12 +359,27 @@
     (define dom-focus (fn (el) (when el (host-call el "focus"))))
     (define
       dom-parse-html
+      ;; Returns a DocumentFragment of the parsed nodes — a real Node, so it can
+      ;; be appendChild-ed as one unit AND queried (querySelector/firstChild).
+      ;; (Was body.childNodes — a NodeList, which appendChild rejects with
+      ;; "Argument 1 does not implement interface Node", silently dropping raw!
+      ;; HTML in the client SX render; dom-query on it in hs-htmx was a no-op too.)
       (fn
         (html)
         (let
           ((parser (host-new "DOMParser"))
-            (doc (host-call parser "parseFromString" html "text/html")))
-          (host-get (host-get doc "body") "childNodes"))))
+            (doc (host-call parser "parseFromString" html "text/html"))
+            (frag (create-fragment)))
+          (let
+            ((body (host-get doc "body")))
+            (let
+              loop
+              ((node (host-get body "firstChild")))
+              (when
+                (not (nil? node))
+                (host-call frag "appendChild" node) ;; appendChild MOVES the node
+                (loop (host-get body "firstChild"))))
+            frag))))
     (define
       dom-listen
       (fn