feat(algo): skip day when candidates < slotsPerDay

tests/algorithm.test.mjs

@@ -154,4 +154,37 @@ function emp(id, constraints = {}) {
   }
 }
 
+// slotsPerDay=2 with only 1 eligible employee → day skipped, listed in skippedDates
+{
+  const employees = [emp('alice')];
+  const result = generatePlan(['2026-04-01'], employees, [], fixed, 2);
+  assert.equal(result.assignments.length, 0, 'no assignments when candidates < slotsPerDay');
+  assert.deepEqual(result.skippedDates, ['2026-04-01'], 'date listed in skippedDates');
+}
+
+// slotsPerDay=1 with 0 candidates → still skipped, listed
+{
+  // 2026-04-01 = Wednesday (3), only employee blocks Wednesday
+  const employees = [emp('alice', { neverDays: [3] })];
+  const result = generatePlan(['2026-04-01'], employees, [], fixed, 1);
+  assert.equal(result.assignments.length, 0, 'no assignments when 0 candidates');
+  assert.deepEqual(result.skippedDates, ['2026-04-01'], 'date listed in skippedDates');
+}
+
+// Mixed: some days fully assigned, some skipped
+{
+  // 2026-04-01 = Wed, 2026-04-02 = Thu
+  // alice can only Wed, bob can always work
+  const employees = [
+    emp('alice', { onlyDays: [3] }),
+    emp('bob')
+  ];
+  const result = generatePlan(['2026-04-01','2026-04-02'], employees, [], fixed, 2);
+  // 2026-04-01: 2 candidates → 2 entries
+  assert.equal(result.assignments.filter(a => a.date === '2026-04-01').length, 2, 'Wed has 2 entries');
+  // 2026-04-02: only bob → skipped
+  assert.equal(result.assignments.filter(a => a.date === '2026-04-02').length, 0, 'Thu skipped');
+  assert.deepEqual(result.skippedDates, ['2026-04-02'], 'Thu in skippedDates');
+}
+
 console.log('All algorithm tests passed.');