Separate custom strategies from Pitaya

[Gusarich]

Right now we have some "custom" strategies in this repository, made specifically for some tasks we had to perform often. Like docs-reviewing stuff.

These should be maintained in different places, and this repository must only ship the most basic, "core" strategies. Perhaps even no strategies at all apart from the simple one, since this tool is mostly oriented on developers for scaling agentic workflows, not on personal coding use.