iris: send tail=true for GetTaskLogs RPC

Fixes #3671 — task logs now return the last N lines instead of the
first N, matching the existing FetchLogs (process logs) behavior.

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

Author: ravwojdyla

lib/iris/dashboard/src/components/shared/LogViewer.vue

@@ -42,6 +42,7 @@ const taskLogState = props.taskId
       id: props.taskId,
       maxTotalLines: tailLines.value || undefined,
       attemptId: selectedAttemptId.value >= 0 ? selectedAttemptId.value : -1,
+      tail: true,
     }))
   : null