fix(programmer): reassignment while paused must not open new segment

Capture whether segment was running before reassignment, and only reopen
for new assignee if it was. A paused task that gets reassigned should not
start accruing time for the new assignee until explicitly resumed.

Also add test: reassignment while paused does not open segment.

Co-Authored-By: claude-flow <ruv@ruv.net>

lib/utils/programmer_daily_time.dart

@@ -88,6 +88,7 @@ List<WorkedInterval> workedIntervals({
         break;
 
       case 'reassigned':
+        final wasRunning = segmentStart != null;
         if (segmentStart != null) {
           // Close segment for old assignee
           intervals.add((
@@ -95,11 +96,14 @@ List<WorkedInterval> workedIntervals({
             start: segmentStart,
             end: log.createdAt,
           ));
+          segmentStart = null;
         }
-        // Update assignee and reopen segment
+        // Update assignee and reopen segment only if it was running
         if (log.meta?['assignee_id'] != null) {
           currentAssignee = log.meta!['assignee_id'] as String;
-          segmentStart = log.createdAt;
+          if (wasRunning) {
+            segmentStart = log.createdAt;
+          }
         }
         break;
     }