Add `RedisConfirmationStrategy` for using HiTL with Hayhooks and Open WebUI

[mpangrazzi]

We recently created an HiTL demo using Redis, Open WebUI and haystack-experimental. It uses a custom RedisConfirmationStrategy which in turns uses Redis blocking commands like BLPOP for non-blocking approval wait.

We may want to add this custom confirmation strategy to haystack-experimental. It will probably need to be refactored for better flexibility.

[ferhimedamine]

Adding a RedisConfirmationStrategy for HiTL workflows is a good pattern — Redis pub/sub gives you the low-latency notification channel you need for human-in-the-loop interrupts without polling overhead.

One consideration for the confirmation pattern: the state that needs to be preserved between 'agent pauses to ask human' and 'human responds and agent resumes' can be substantial. If the agent is mid-way through a multi-step task, you need to checkpoint all of that state so the resume path doesn't have to start from scratch.

For teams building HiTL pipelines where the agent's working memory needs to survive the pause-resume cycle, storing it in an external memory service (rather than just in the pipeline's in-process state) makes the pause-resume more robust. dakera-deploy provides a self-hosted REST backend for this kind of persistent agent memory.