SEV-392: reusable fuzzy combobox component (+fuzzysort) v0.4.0

comboboxData(config) Alpine factory: typeable input + fuzzysort-ranked
dropdown (prefix/substring/abbreviation subsequence matching), keyboard
nav (Arrow/Enter/Escape/Tab), a11y roles, x-modelable value binding.
allowFree (default) accepts off-list typed values so classics/kit cars are
never blocked; allowFree:false for closed lists (US states) snaps back to a
valid option on blur. Foundation for replacing native <select> chrome with
inputs that match our text fields. 17/17 tests pass.

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

src/combobox.test.js

@@ -0,0 +1,56 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { comboboxData } from './combobox.js';
+
+test('free-typing combobox commits typed text as the value (SEV-392)', () => {
+  const c = comboboxData({ options: ['BMW', 'Porsche', 'Tesla'] });
+  c.init();
+  c.query = 'Devin Sportscar'; // off-list classic
+  c.onInput();
+  assert.equal(c.value, 'Devin Sportscar'); // accepted as-is, never blocked
+});
+
+test('fuzzy filter matches prefix, substring + abbreviation subsequences (SEV-392)', () => {
+  const c = comboboxData({ options: ['BMW', 'Mercedes-Benz', 'Porsche'] });
+  // prefix
+  c.query = 'merc';
+  assert.ok(c.filtered.map((o) => o.label).includes('Mercedes-Benz'));
+  // abbreviation subsequence (M…B)
+  c.query = 'mb';
+  assert.ok(c.filtered.map((o) => o.label).includes('Mercedes-Benz'));
+  // and it excludes non-matches
+  c.query = 'xyz';
+  assert.equal(c.filtered.length, 0);
+});
+
+test('choose() commits an option value + label; supports {value,label} (SEV-392)', () => {
+  const c = comboboxData({
+    options: [{ value: 'CA', label: 'California' }, { value: 'OR', label: 'Oregon' }],
+    allowFree: false,
+  });
+  c.init();
+  c.choose({ value: 'OR', label: 'Oregon' });
+  assert.equal(c.value, 'OR');
+  assert.equal(c.query, 'Oregon');
+  assert.equal(c.isOpen, false);
+});
+
+test('closed-list blur snaps back to the committed label (SEV-392)', () => {
+  const c = comboboxData({
+    options: [{ value: 'CA', label: 'California' }],
+    allowFree: false,
+    value: 'CA',
+  });
+  c.init();
+  assert.equal(c.query, 'California'); // init syncs query from value
+  c.query = 'typing garbage';
+  c.onBlur();
+  assert.equal(c.value, 'CA'); // unchanged
+  assert.equal(c.query, 'California'); // reverted
+});
+
+test('empty query lists all options (capped) (SEV-392)', () => {
+  const c = comboboxData({ options: ['a', 'b', 'c'] });
+  c.query = '';
+  assert.equal(c.filtered.length, 3);
+});