fix(fusion_clock): code-review hardening [19.0.5.0.1]

- _cron_generate: per-rule savepoint isolation (one bad rule can't abort the
  whole daily batch)
- fclk_attach_recurrence: clear an existing recurrence first (no orphaned rule
  generating forever)
- fclk_apply_planner_cell: collapse split rows (search was limit=1 after the
  UNIQUE drop, orphaning extras)
- fclk_release_shift: reject non-posted/open shifts (raw-POST guard)
- delete_open_shift: report success=false when nothing was deleted + JS surfaces it
- _generate: log before removing an empty recurrence
Tests added for collapse, re-attach, draft-release.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

fusion_clock/tests/test_shift_planner.py

@@ -67,6 +67,23 @@ class TestShiftPlannerModels(TransactionCase):
         self.assertEqual(schedule.planned_hours, 8.0)
         self.assertEqual(self.Schedule.fclk_hours_display(schedule.planned_hours), '8:00')
 
+    def test_planner_cell_collapses_split_rows(self):
+        # Editing a day's planner cell must collapse any split rows into one
+        # (the planner cell is the authoritative single entry for the day).
+        d = date(2026, 1, 20)
+        self.Schedule.create({
+            'employee_id': self.employee.id, 'schedule_date': d,
+            'start_time': 8.0, 'end_time': 12.0, 'state': 'posted'})
+        self.Schedule.create({
+            'employee_id': self.employee.id, 'schedule_date': d,
+            'start_time': 13.0, 'end_time': 17.0, 'state': 'posted'})
+        self.assertEqual(self.Schedule.search_count([
+            ('employee_id', '=', self.employee.id), ('schedule_date', '=', d)]), 2)
+        self.Schedule.fclk_apply_planner_cell(self.employee, d, {'input': '9-5'})
+        self.assertEqual(self.Schedule.search_count([
+            ('employee_id', '=', self.employee.id), ('schedule_date', '=', d)]), 1,
+            "planner edit should collapse split rows to one")
+
     def test_overnight_range_is_accepted(self):
         # Overnight shifts (end on/before start) are supported as of 19.0.5.0.0.
         sch = self.Schedule.create({