fix: defer stuck-kill requeue to executor finally block to prevent race

When the stuck task detector killed a task and immediately called
moveTask("todo"), the scheduler could re-dispatch the task before the
old execution's finally block cleared this.executing. The new execute()
call hit the guard and silently returned, stranding the task in
"in-progress" with no active session or worktree (seen on FN-810/FN-912).

Move the requeue responsibility from StuckTaskDetector.killAndRetry to
the executor's finally block, which runs after this.executing.delete().
The beforeRequeue budget check now runs before session.dispose() and its
result is passed via StuckTaskEvent.shouldRequeue → markStuckAborted().

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/cli/src/commands/dashboard.ts

@@ -578,12 +578,12 @@ export async function runDashboard(port: number, opts: { paused?: boolean; dev?:
     const stuckTaskDetector = new StuckTaskDetector(store, {
       beforeRequeue: (taskId) => selfHealing.checkStuckBudget(taskId),
       onStuck: (event) => {
-        executorRef.current?.markStuckAborted(event.taskId);
+        executorRef.current?.markStuckAborted(event.taskId, event.shouldRequeue);
         console.log(
           `[engine] ⚠ ${event.taskId} stuck (${event.reason}) — ` +
           `no progress for ${Math.round(event.noProgressMs / 60_000)}min, ` +
           `${event.activitySinceProgress} events since last progress — ` +
-          `terminated, will retry`,
+          `terminated, ${event.shouldRequeue ? "will retry" : "budget exhausted"}`,
         );
       },
     });