Web pages: browsers are made at once, so none outlives its view (M-12)

make_browsers creates each browser synchronously and adopts it in the
same call, so no view waits on a browser: it leaves before creation
(skipped) or has a browser to close. The late-close branch in
on_after_created is gone. webprobe drops 5 views before the pump and
10 within 27 ms; webview.sh wants all 35 freed before the hold.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/scripts/webview.sh

@@ -65,11 +65,12 @@ probe=
 out=$(cat "$work/out")
 for want in "probe: value=你好a" "probe: focused=text" "probe: zoom=1.25" "probe: stayed" \
   "probe: outside=false" "probe: network=refused" "probe: udp=silent" "probe: rtc=undefined" "probe: main failed" "probe: hash loaded" "probe: missing failed" \
-  "probe: closed 20"; do
+  "probe: closed 20" "probe: dropped 5 unmade, 10 early"; do
   grep -qxF "$want" <<<"$out" || fail "expected '$want', got: $out"
 done
 grep -qE '^probe: fg=rgba\([0-9]+, [0-9]+, [0-9]+, ' <<<"$out" || fail "no theme token: $out"
-freed=$(grep -c "a page's memory is freed" "$work/err" || true)
-[ "$freed" -ge 20 ] || fail "only $freed of 20 closed pages freed their memory"
+# Freed before the hold: 20 closed, 5 unmade, 10 early.
+freed=$(awk "/probe: hold/ { exit } /a page's memory is freed/ { n++ } END { print n + 0 }" "$work/err")
+[ "$freed" -ge 35 ] || fail "only $freed of 35 closed pages freed their memory"
 ! grep -q "panicked" "$work/err" || fail "panics: $(grep -m3 panicked "$work/err")"
 echo "ok: webview (marker share $share, $freed pages freed)"