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/tests/broker/expand.test.ts

@@ -140,6 +140,42 @@ describe('expandOccurrences', () => {
     })
   })
 
+  describe('Non-recurring DURATION-only event — single-duration.ics', () => {
+    it('BUG-1 regression: non-recurring event with DURATION but no DTEND has end strictly after start', () => {
+      // Real Fastmail events use DURATION (not DTEND). Before the fix, the NON-RECURRING branch
+      // used getFirstPropertyValue('dtend') ?? dtstart, which returned dtstart when DTEND was absent,
+      // producing zero-duration occurrences (invisible in week/day views).
+      const rawVevent = loadFixture('single-duration.ics')
+      const windowStart = new Date('2026-06-01T00:00:00Z')
+      const windowEnd = new Date('2026-07-01T00:00:00Z')
+
+      const occurrences = expandOccurrences(
+        rawVevent,
+        windowStart,
+        windowEnd,
+        1,
+        'My Calendar',
+        1,
+        '#4A90D9',
+        false,
+      )
+
+      expect(occurrences.length).toBe(1)
+
+      const occ = occurrences[0]
+      expect(occ.allDay).toBe(false)
+
+      // Parse both via Temporal.ZonedDateTime and assert end > start
+      const startZdt = Temporal.ZonedDateTime.from(occ.start)
+      const endZdt = Temporal.ZonedDateTime.from(occ.end)
+      expect(Temporal.ZonedDateTime.compare(endZdt, startZdt)).toBeGreaterThan(0)
+
+      // Verify the actual duration is correct: DURATION:PT1H → end is 1 hour after start
+      expect(endZdt.hour - startZdt.hour).toBe(1)
+      expect(endZdt.minute).toBe(startZdt.minute)
+    })
+  })
+
   describe('Cross-contract: expand output → Temporal.ZonedDateTime.from (regression guard)', () => {
     it('timed event start/end strings from weekly-dst.ics parse via Temporal.ZonedDateTime.from without throwing', () => {
       // This is the integration test that was missing. It takes the actual serializeTime output