feat(FN-4393): docs, changeset, and verification fixes

Commits merged:
- feat(FN-4393): complete Step 6 — docs, changeset, and verification fixes

Files changed:
packages/core/src/types.ts             | 12 ++++++------
 packages/engine/src/agent-heartbeat.ts |  5 ++++-
 2 files changed, 10 insertions(+), 7 deletions(-)

Fusion-Task-Id: FN-4393

Fusion-Task-Lineage: 3615215d-9caa-4402-9258-a5a5de137dd6

packages/engine/src/agent-heartbeat.ts

@@ -2048,10 +2048,13 @@ export class HeartbeatMonitor {
 
         if (priorMemoryMode !== resolvedMemoryMode.mode) {
           const from = priorMemoryMode ? priorMemoryMode : "(initial)";
+          const runContextTaskId = typeof run.contextSnapshot?.taskId === "string"
+            ? run.contextSnapshot.taskId
+            : undefined;
           try {
             await this.store.appendRunLog(agentId, run.id, {
               timestamp: new Date().toISOString(),
-              taskId: taskId ?? run.taskId ?? "heartbeat",
+              taskId: taskId ?? runContextTaskId ?? "heartbeat",
               type: "text",
               text: `Agent memory inclusion mode: ${from} → ${resolvedMemoryMode.mode} (source: ${resolvedMemoryMode.source})`,
             });