HS parser/compiler/mock: fix put positions, add CSS properties

Parser:
- Skip optional "the" in "at the start/end of" put targets
- Handle "style" token type in parse-add-cmd for *prop:value syntax

Compiler:
- Add set-style dispatch → dom-set-style for CSS property additions

Mock DOM:
- Position-aware insertAdjacentHTML: afterbegin prepends, beforeend appends
- Sync textContent after insertAdjacentHTML mutations

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

hosts/ocaml/bin/run_tests.ml

@@ -1985,12 +1985,26 @@ let run_spec_tests env test_files =
            Hashtbl.replace r "right" (Number 100.0); Hashtbl.replace r "bottom" (Number 100.0);
            Dict r
          | "insertAdjacentHTML" ->
-           (* Simplified: coerce value to string and append to innerHTML *)
+           (* Position-aware insertion, coerce value to string *)
            (match rest with
-            | [String _pos; value] ->
+            | [String pos; value] ->
               let html = match dom_stringify value with String s -> s | _ -> "" in
               let cur = match Hashtbl.find_opt d "innerHTML" with Some (String s) -> s | _ -> "" in
-              Hashtbl.replace d "innerHTML" (String (cur ^ html)); Nil
+              let new_html = match pos with
+                | "afterbegin" -> html ^ cur    (* prepend *)
+                | _ -> cur ^ html               (* beforeend / default: append *)
+              in
+              Hashtbl.replace d "innerHTML" (String new_html);
+              (* Sync textContent *)
+              let buf = Buffer.create (String.length new_html) in
+              let in_tag = ref false in
+              String.iter (fun c ->
+                if c = '<' then in_tag := true
+                else if c = '>' then in_tag := false
+                else if not !in_tag then Buffer.add_char buf c
+              ) new_html;
+              Hashtbl.replace d "textContent" (String (Buffer.contents buf));
+              Nil
             | _ -> Nil)
          | "showModal" | "show" ->
            Hashtbl.replace d "open" (Bool true);