fix(FN-1300): capture agent run output in heartbeat and step sessions

- Wire AgentLogger into heartbeat runs, including tool/text callbacks and stdout excerpts on run records
- Persist heartbeat context taskId snapshots earlier and ensure logger flushes on success and failure paths
- Pass TaskStore into StepSessionExecutor and flush per-attempt agent logs in finally cleanup
- Expand heartbeat and step-session tests to verify log persistence and flush behavior, and add a patch changeset for @gsxdsm/fusion

packages/engine/src/executor.ts

@@ -854,6 +854,7 @@ export class TaskExecutor {
         executorLog.log(`${task.id}: using step-session mode (maxParallel=${settings.maxParallelSteps ?? 2})`);
 
         const stepExecutor = new StepSessionExecutor({
+          store: this.store,
           taskDetail: detail,
           worktreePath,
           rootDir: this.rootDir,