HS: transition query-ref + multi-prop (+2 tests)

Three parts: (a) parser `collect-transitions` recognises `style`
tokens (`*prop`) as a continuation, so
`transition *width from A to B *height from A to B` chains both
transitions instead of dropping the second. (b) Mock `El` class gets
`nextSibling`/`previousSibling` (plus `*ElementSibling` aliases) so
`transition *W of the next <span/>` can resolve the next-sibling
target via host-get. (c) Generator pattern for
`const X = await evaluate(() => { const el = document.querySelector(SEL);
el.dispatchEvent(new Event(NAME, ...)); return ... })`; optionally
prefixed by a destructuring assignment and allowing trailing
`expect(...).toBe(...)` junk because `_body_statements` only splits on
`;` at depth 0.

Remaining `can use initial to transition to original value` needs
`on click N` count-filtered events (same mock-sync block as cluster 13).

Suite hs-upstream-transition: 13/17 → 15/17. Smoke 0-195: 162/195
unchanged.

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

tests/hs-run-filtered.js

@@ -52,6 +52,10 @@ class El {
   contains(o) { if(o===this)return true; for(const c of this.children)if(c===o||c.contains(o))return true; return false; }
   cloneNode(d) { const e=new El(this.tagName.toLowerCase()); Object.assign(e.attributes,this.attributes); e.id=this.id; e.className=this.className; e.classList._sync(this.className); for(const k of Object.keys(this.style)){if(typeof this.style[k]!=='function')e.style[k]=this.style[k];} e.textContent=this.textContent; e.innerHTML=this.innerHTML; e.value=this.value; if(d)for(const c of this.children)e.appendChild(c.cloneNode(true)); return e; }
   focus(){} blur(){} click(){this.dispatchEvent(new Ev('click',{bubbles:true}));} remove(){if(this.parentElement)this.parentElement.removeChild(this);}
+  get nextSibling(){const p=this.parentElement;if(!p)return null;const i=p.children.indexOf(this);return i>=0&&i<p.children.length-1?p.children[i+1]:null;}
+  get nextElementSibling(){return this.nextSibling;}
+  get previousSibling(){const p=this.parentElement;if(!p)return null;const i=p.children.indexOf(this);return i>0?p.children[i-1]:null;}
+  get previousElementSibling(){return this.previousSibling;}
   reset(){
     // Form reset: walk descendants, restore defaultValue / defaultChecked /
     // defaultSelected.