fix(memory): block turns when required recall times out

[memand]

Summary

Makes automatic memory-recall timeouts visible, controlled, and fail closed.

Behavior

When required automatic memory recall exceeds its bounded timeout:

• no main-model call or agent response is produced without recalled memories;
• a concise error explains that the response was blocked;
• the failed recall task is cleared;
• HandledException terminates the turn through the framework's controlled exception path;
• asyncio.CancelledError still propagates unchanged.

The wait extension now also evaluates a completed recall task, so a timeout that finished before the wait extension runs is not silently missed.

Validation

/opt/venv-a0/bin/python -m unittest -v tests.test_memory_recall_wait
Ran 3 tests ... OK

Tests cover pending timeout blocking, completed timeout blocking, and cancellation propagation.

Fixes #1848.