HS reset/first/last: defaultValue tracking, list-of-elements reset, find().first|last

Mock DOM:
- El now tracks defaultValue/defaultChecked/defaultSelected and a reset()
  method that walks descendant form controls, restoring them.
- setAttribute(value|checked|selected) sets the matching default-* too, so
  the initial HTML state can be restored later.
- parseHTMLFragments + _setInnerHTML capture a textarea's textContent as
  its value AND defaultValue.

Generator (pw-body):
- add_action / add_assertion extract .first() / .last() / .nth(N) modifiers
  into (nth (dom-query-all …) i) or a (let ((_all …)) (nth _all (- … 1)))
  tail so multi-match helpers hit the right element.

Compiler:
- emit-reset! with a .<class>/.<sel> query target now compiles to hs-query-all
  so 'reset .resettable' resets every matching control (not just the first).

Net: reset 1→8 (100%).

shared/static/wasm/sx/hs-compiler.sx

@@ -1835,7 +1835,14 @@
               ((= head (quote select!))
                 (list (quote hs-select!) (hs-to-sx (nth ast 1))))
               ((= head (quote reset!))
-                (list (quote hs-reset!) (hs-to-sx (nth ast 1))))
+                (let
+                  ((raw-tgt (nth ast 1)))
+                  (cond
+                    ((and (list? raw-tgt) (= (first raw-tgt) (quote query)))
+                      (list
+                        (quote hs-reset!)
+                        (list (quote hs-query-all) (nth raw-tgt 1))))
+                    (true (list (quote hs-reset!) (hs-to-sx raw-tgt))))))
               ((= head (quote default!))
                 (let
                   ((tgt-ast (nth ast 1))