fix(timer): count-to-end events absorb overtime in expected end times

The server computed rundown/group expected end times as
`expectedStart + duration`, ignoring `countToEnd`. For a count-to-end
last event running in overtime this pushed the projected end far past
(or before) its fixed end time, producing nonsensical values (e.g. a
negative expected rundown end) and leaving group/flag readouts stuck on
"due". It also never broke the link chain after a count-to-end event,
unlike the client.

A count-to-end event ends at its fixed end time regardless of preceding
overtime (matching `getExpectedFinish` for the running timer), so its
expected end should pin to the planned end and absorb the accumulated
offset.

- add shared `getExpectedEnd` helper in ontime-utils that pins
  count-to-end events to their planned end
- use it in `getExpectedTimes` for both rundown and group end
- break the `isLinkedToLoaded` chain after a count-to-end event in
  `loadGroupFlagAndEnd`, mirroring the client metadata logic
- delegate the client's `getExpectedTimesFromExtendedEvent` to the shared
  helper to remove the duplicated formula that caused the drift
- add unit and runtime-state tests covering overtime absorption and the
  chain break

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ACGuFWt5aN7Fv3AkYXgxLm

apps/client/src/common/utils/time.ts

@@ -4,6 +4,7 @@ import {
   MILLIS_PER_MINUTE,
   MILLIS_PER_SECOND,
   formatFromMillis,
+  getExpectedEnd,
   getExpectedStart,
 } from 'ontime-utils';
 
@@ -172,13 +173,15 @@ export function getExpectedTimesFromExtendedEvent(
 ) {
   if (event === null) return { expectedStart: 0, timeToStart: 0, expectedEnd: 0, plannedEnd: 0 };
 
+  const expectedStartState = {
+    totalGap: event.totalGap,
+    isLinkedToLoaded: event.isLinkedToLoaded,
+    ...state,
+  };
+
   const expectedStart = getExpectedStart(
     { timeStart: event.timeStart, delay: event.delay, dayOffset: event.dayOffset },
-    {
-      totalGap: event.totalGap,
-      isLinkedToLoaded: event.isLinkedToLoaded,
-      ...state,
-    },
+    expectedStartState,
   );
 
   const plannedEnd = event.timeStart + event.duration + event.delay;
@@ -186,9 +189,7 @@ export function getExpectedTimesFromExtendedEvent(
   return {
     expectedStart,
     timeToStart: expectedStart - state.clock,
-    expectedEnd: event.countToEnd
-      ? Math.max(expectedStart + event.duration, plannedEnd)
-      : expectedStart + event.duration,
+    expectedEnd: getExpectedEnd(event, expectedStartState),
     plannedEnd,
   };
 }