feat(bal): export calendar .ics as separate reminder events (v0.3.7)

- open_or_save_calendar(): emit one VEVENT per reminder instead of a single
  event with VALARM blocks. Dates come from compute_reminder_offsets(), spread
  across the check-alive period, with the LAST event one day before the
  locktime. Unique UID per event (bal-<wallet>-<offset>d) and numbered
  summaries ' (reminder N/total)'.
- Removed the now-unused create_alarms() method (no more VALARM).
- Default save filename changed from will_event.ics to BAL_will_event.ics.
- common.py: added timedelta to the datetime import.
- plugin_base.py: updated the NUM_REMINDERS comment for the new behaviour.
- tests: replaced the VALARM E1 test with test_e1_build_separate_events_for_giovanna.
- Bumped version to 0.3.7 (4 files) and added CHANGELOG entry #13.

Tests: 239 passed. ruff: no new errors.

bal/core/plugin_base.py

@@ -91,7 +91,7 @@ class BalPlugin(BasePlugin):
     """
 
     _version = None
-    __version__ = "0.3.6"  # AUTOMATICALLY GENERATED DO NOT EDIT
+    __version__ = "0.3.7"  # AUTOMATICALLY GENERATED DO NOT EDIT
 
     # Command used to open an .ics calendar file, per operating system.
     default_app = {
@@ -181,12 +181,13 @@ class BalPlugin(BasePlugin):
         # stay display-only outside the wizard unless the user opts in.
         self.EDITABLE_DATES = BalConfig(config, "bal_editable_dates", False)
 
-        # NUM_REMINDERS (Group D / D1): how many reminder alarms (VALARM) the
-        # exported .ics calendar event should contain. The reminders are spread
-        # uniformly across the check-alive period and always fall BEFORE the
-        # delivery deadline. Default 3; the settings dialog caps it at 5 and the
-        # alarm builder additionally limits it to at most one alarm per available
-        # day.
+        # NUM_REMINDERS (Group D / D1): how many SEPARATE reminder events the
+        # exported .ics calendar should contain. Each reminder becomes its own
+        # VEVENT (its own date in the calendar). The dates are spread uniformly
+        # across the check-alive period and the LAST one always falls one day
+        # before the delivery deadline (locktime). Default 3; the settings
+        # dialog caps it at 5 and the date builder additionally limits it to at
+        # most one event per available day.
         self.NUM_REMINDERS = BalConfig(config, "bal_num_reminders", 3)
 
         self.NO_WILLEXECUTOR = BalConfig(config, "bal_no_willexecutor", True)