test: add missing tests for companyClosures, lowPriorityDays, and manual flag

tests/algorithm.test.mjs

@@ -99,4 +99,26 @@ function emp(id, constraints = {}) {
   assert.equal(result[0].employeeId, 'bob', 'bob (0 history) beats alice (5 history)');
 }
 
+// companyClosures excluded from workdays
+{
+  const days = getWorkdays(2026, 4, [], ['2026-04-01']);
+  assert.equal(days.length, 21, 'Closure reduces count by 1');
+  assert.ok(!days.includes('2026-04-01'), 'Closure date excluded');
+}
+
+// lowPriorityDays reduces score — bob without penalty wins over alice with penalty
+{
+  // 2026-04-01 = Wednesday (3); alice has lowPriorityDays on Wednesday
+  // Both have same history (0) — alice's score gets -5 penalty, bob wins
+  const employees = [emp('alice', {lowPriorityDays:[3]}), emp('bob')];
+  const result = generatePlan(['2026-04-01'], employees, [], fixed);
+  assert.equal(result[0].employeeId, 'bob', 'alice low priority on Wednesday → bob wins');
+}
+
+// manual: false on auto-assigned entries
+{
+  const result = generatePlan(['2026-04-01'], [emp('alice')], [], fixed);
+  assert.equal(result[0].manual, false, 'auto-assignment sets manual: false');
+}
+
 console.log('All algorithm tests passed.');