HS: extend parser/runtime + new node test runner; ignore test-results/

- Parser: `--` line comments, `|` op, `result` → `the-result`, query-scoped
  `<sel> in <expr>`, `is a/an <type>` predicate, multi-`as` chaining with `|`,
  `match`/`precede` keyword aliases, `[attr]` add/toggle, between attr forms
- Runtime: per-element listener registry + hs-deactivate!, attr toggle
  variants, set-inner-html boots subtree, hs-append polymorphic on
  string/list/element, default? / array-set! / query-all-in / list-set
  via take+drop, hs-script idempotence guard
- Integration: skip reserved (me/it/event/you/yourself) when collecting vars
- Tokenizer: emit `--` comments and `|` op
- Test framework + conformance runner updates; new tests/hs-run-filtered.js
  (single-process Node runner using OCaml VM step-limit to bound infinite
  loops); generate-sx-conformance-dev.py improvements
- mcp_tree.ml + run_tests.ml: harness extensions
- .gitignore: top-level test-results/ (Playwright artifacts)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

spec/tests/test-hs-diag.sx

@@ -4,7 +4,9 @@
     "put into #id compiled"
     (let
       ((sx (hs-to-sx-from-source "on click put \"foo\" into #d1")))
-      (assert= (serialize sx) "SHOW")))
+      (assert=
+        (serialize sx)
+        "(hs-on me \"click\" (fn (event) (hs-set-inner-html! (hs-query-first \"#d1\") \"foo\")))")))
   (deftest
     "put into #id works"
     (let