fusion/.changeset/merge-queue-priority.md

@runfusion/fusion

@runfusion/fusion
patch

Apply task priority across all Fusion scheduling paths so urgent work overtakes older low-priority work — including the merge queue, which previously merged tasks strictly FIFO.

• The auto-merge queue now picks the highest-priority eligible task each iteration (urgent → high → normal → low, then createdAt ASC, then id ASC). Manual onMerge resolvers still run before auto-merges so awaited callers aren't starved.
• Startup, periodic, global-unpause, and engine-unpause sweeps now sort their listTasks result by priority before enqueueing, so the first task picked up by drainMergeQueue's single-item fast path is the highest-priority eligible one rather than the oldest. All four sweeps share a new enqueueEligibleInReviewTasks helper.
• Hardened the picker against concurrent queue mutation: it now re-locates the chosen task via indexOf after awaiting getTask, so a stop() clear or pause-handler removal that lands during the await can't splice out the wrong sibling. Drain and picker both re-check shuttingDown after the awaits to avoid starting a merge whose queue entry was already cleared.
• Triage and todo→in-progress scheduling already used the shared sortTasksByPriorityThenAgeAndId comparator and continue to apply dependency, overlap, and worktree constraints after the priority sort.