SEV-408: combobox displayValue option (show code, search by label) v0.5.0

When displayValue:true, the input shows the selected option's value (e.g. a
state code "TX") while the dropdown stays label-searchable ("Texas") — for a
field searched by name but displayed compactly. Backward-compatible
(default false). 20/20 tests pass.

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

src/combobox.js

@@ -46,6 +46,10 @@ export function comboboxData(config = {}) {
   const allowFree = config.allowFree !== false;
   const fuzzy = config.fuzzy !== false;
   const limit = config.limit || 50;
+  // displayValue: after selecting, show the option's VALUE (e.g. a state code
+  // "TX") in the input instead of its LABEL ("Texas"), while the dropdown stays
+  // label-searchable. Lets a field be searched by name but display the code.
+  const displayValue = config.displayValue === true;
 
   return {
     value: config.value ?? '',
@@ -89,7 +93,8 @@ export function comboboxData(config = {}) {
         return;
       }
       const match = this._options.find((o) => o.value === String(v));
-      this.query = match ? match.label : allowFree ? String(v) : '';
+      if (match) this.query = displayValue ? match.value : match.label;
+      else this.query = allowFree ? String(v) : '';
     },
 
     get filtered() {
@@ -121,7 +126,7 @@ export function comboboxData(config = {}) {
 
     choose(opt) {
       this.value = opt.value;
-      this.query = opt.label;
+      this.query = displayValue ? opt.value : opt.label;
       this.close();
     },