fix(events): null end_dt no longer matches events outside the window

services/events.py::list_events treated any event with end_dt IS NULL
as perpetually matching, so a point-event created last week would be
returned as "happening today" whenever the briefing or list_events
tool queried today's window. That manifested as briefings claiming
past events were scheduled for the current day.

Split the null-end branch: point events now only match when start_dt
falls within [date_from, date_to]. Events with an end_dt continue to
use standard overlap logic.

This bug affected both the legacy briefing synthesis and the agentic
list_events tool path, since both call the same events service.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/fabledassistant/services/events.py

@@ -7,7 +7,7 @@ import uuid
 from datetime import datetime, timedelta, timezone
 
 from dateutil.rrule import rrulestr
-from sqlalchemy import or_, select
+from sqlalchemy import and_, or_, select
 
 from fabledassistant.models import async_session
 from fabledassistant.models.event import Event
@@ -85,19 +85,30 @@ async def list_events(
     dicts (same shape as Event.to_dict()).
     """
     async with async_session() as session:
+        # Match strategy:
+        #   - Recurring events: fetch all, expand via rrule below.
+        #   - Non-recurring with an end_dt: standard overlap — starts before
+        #     date_to and ends after date_from.
+        #   - Non-recurring with no end_dt: treat as a point event at
+        #     start_dt, include only if start_dt falls within the window.
+        #     (Previously this branch matched any event with a null end_dt,
+        #     returning all past events as "happening today".)
         result = await session.execute(
             select(Event).where(
                 Event.user_id == user_id,
-                # Base window: non-recurring events must overlap range;
-                # recurring events always need to be fetched so they can be expanded.
                 or_(
                     Event.recurrence.isnot(None),
-                    Event.start_dt <= date_to,
-                ),
-                or_(
-                    Event.end_dt.is_(None),
-                    Event.end_dt >= date_from,
-                    Event.recurrence.isnot(None),
+                    and_(
+                        Event.recurrence.is_(None),
+                        Event.start_dt <= date_to,
+                        or_(
+                            Event.end_dt >= date_from,
+                            and_(
+                                Event.end_dt.is_(None),
+                                Event.start_dt >= date_from,
+                            ),
+                        ),
+                    ),
                 ),
             ).order_by(Event.start_dt)
         )