[BUG] Durable agent run waits for thread title generation before it finishes

Describe the bug

Agent.generate() / Agent.stream() generate the thread title fire-and-forget ("so generate()/stream() stay fast", agent.ts). The durable path awaits it: runDurableFinishSideEffects in packages/core/src/agent/durable/workflows/finalize-run.ts does await registryEntry.generateThreadTitle(titleArgs) before the workflow's final step returns, so the run's finish event waits for one extra model call.

Impact

With generateTitle enabled, the first turn of every new thread ends seconds after its answer was already written. Measured on a deployed durable agent with internal spans: map-final-output 4.1 s, of which the title model call is 3.3 s, for a one-word answer.

Expected behavior

Same as the non-durable agent: start title generation in the background, log a failure, never block the finish.

Environment

@mastra/core main (d5307908), also 1.63.2.