fix(02): correct DURATION-only event end in expand.ts (BUG 1)

- Replace dtend ?? dtstart with event.endDate which handles DURATION-only VEVENTs
- Add positive-duration guard (PT30M / P1D) to both non-recurring and recurring branches
- Add single-duration.ics fixture and regression test asserting end > start for DURATION-only events

apps/api/src/broker/expand.ts

@@ -207,9 +207,22 @@ export function expandOccurrences(
   // --- 4. Non-recurring event: single occurrence check ---
   if (!event.isRecurring()) {
     if (dtstart.compare(rangeStart) >= 0 && dtstart.compare(rangeEnd) < 0) {
-      const dtend = (vevent.getFirstPropertyValue('dtend') as ICAL.Time | null) ?? dtstart
+      // Use ICAL.Event.endDate which derives end from DTEND, or DTSTART+DURATION, or sensible default.
+      // Do NOT use getFirstPropertyValue('dtend') directly — events with only DURATION set return null,
+      // producing zero-duration occurrences (BUG 1).
+      let occEnd: ICAL.Time = (event.endDate ?? dtstart) as ICAL.Time
+
+      // Positive-duration guard: ensure timed events have non-zero height in Schedule-X.
+      if (!allDay && occEnd.compare(dtstart) <= 0) {
+        occEnd = dtstart.clone()
+        occEnd.addDuration(ICAL.Duration.fromString('PT30M'))
+      } else if (allDay && occEnd.compare(dtstart) <= 0) {
+        occEnd = dtstart.clone()
+        occEnd.addDuration(ICAL.Duration.fromString('P1D'))
+      }
+
       const start = serializeTime(dtstart, allDay)
-      const end = serializeTime(dtend, allDay)
+      const end = serializeTime(occEnd, allDay)
       occurrences.push({
         id: makeOccurrenceId(uid, dtstart),
         uid,
@@ -240,9 +253,18 @@ export function expandOccurrences(
 
     // Compute occurrence end from event duration
     const duration = event.duration
-    const occEnd = next.clone()
+    let occEnd = next.clone()
     occEnd.addDuration(duration)
 
+    // Positive-duration guard: same logic as non-recurring branch above.
+    if (!allDay && occEnd.compare(next) <= 0) {
+      occEnd = next.clone()
+      occEnd.addDuration(ICAL.Duration.fromString('PT30M'))
+    } else if (allDay && occEnd.compare(next) <= 0) {
+      occEnd = next.clone()
+      occEnd.addDuration(ICAL.Duration.fromString('P1D'))
+    }
+
     const start = serializeTime(next, allDay)
     const end = serializeTime(occEnd, allDay)