HS tests: innerHTML/textContent clears children in mock DOM

Setting innerHTML="" on a mock element now detaches and removes all
children, matching browser behavior. Previously hs-cleanup! (which
sets body.innerHTML="") left stale children attached, causing
querySelector to find elements from prior tests.

Also clears children when textContent is set (browser behavior).

375 → 393/831 HS tests (+18).

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

hosts/ocaml/bin/run_tests.ml

@@ -1663,12 +1663,29 @@ let run_spec_tests env test_files =
       in
       Hashtbl.replace d key stored;
       (* Side effects for special keys *)
-      (if key = "className" then
+      (match key with
-         match Hashtbl.find_opt d "classList" with
+       | "className" ->
-         | Some (Dict cl) ->
+         (match Hashtbl.find_opt d "classList" with
-           (* classList sub-dict doesn't store classes — they live in className *)
+          | Some (Dict _cl) -> () (* classes live in className *)
-           ignore cl
+          | _ -> ())
-         | _ -> ());
+       | "innerHTML" ->
+         (* Setting innerHTML clears children (like a real browser) *)
+         (match stored with
+          | String "" ->
+            (* Detach children *)
+            let kids = match Hashtbl.find_opt d "children" with Some (List l) -> l | _ -> [] in
+            List.iter (fun c -> match c with Dict cd ->
+              Hashtbl.replace cd "parentElement" Nil;
+              Hashtbl.replace cd "parentNode" Nil | _ -> ()) kids;
+            Hashtbl.replace d "children" (List []);
+            Hashtbl.replace d "childNodes" (List []);
+            Hashtbl.replace d "textContent" (String "")
+          | _ -> ())
+       | "textContent" ->
+         (* Setting textContent clears children *)
+         Hashtbl.replace d "children" (List []);
+         Hashtbl.replace d "childNodes" (List [])
+       | _ -> ());
       stored
     | _ -> Nil);