SEV-392: combobox setOptions() for reactive parent-fed option lists

Passing a parent component's reactive array into the nested combobox x-data
needs x-effect="setOptions(vpicMakes)" — a plain closure over the parent
scope doesn't track Alpine updates. Falls back to config.options for static
lists. 18/18 tests pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/combobox.js

@@ -53,6 +53,7 @@ export function comboboxData(config = {}) {
     isOpen: false,
     highlighted: -1,
     placeholder: config.placeholder || '',
+    _opts: null, // set reactively via setOptions(); see _options getter
 
     init() {
       this.syncQueryFromValue();
@@ -66,8 +67,19 @@ export function comboboxData(config = {}) {
       }
     },
 
+    // setOptions lets a parent feed reactive option lists in via x-effect —
+    // e.g. x-effect="setOptions(vpicMakes)" — which is the reliable way to
+    // pass a parent component's reactive array into this nested x-data (a
+    // plain closure over the parent scope would NOT track updates). Falls back
+    // to config.options when never called (static lists).
+    setOptions(raw) {
+      this._opts = normalizeOptions(raw);
+      // a shrinking list shouldn't leave a stale highlight selected
+      if (this.highlighted >= this._opts.length) this.highlighted = -1;
+    },
+
     get _options() {
-      return normalizeOptions(config.options);
+      return this._opts != null ? this._opts : normalizeOptions(config.options);
     },
 
     syncQueryFromValue() {